Tetrahydroisoquinolines and intermediates therefor

ABSTRACT

Disclosed are processes for preparing tetrahydroisoquinolines, intermediates useful in the preparation of tetrahydroisoquinolines, processes for preparing such intermediates, and a crystalline form of 6-[(4S)-2-methyl-4-(naphthyl)-1,2,3,4-tetrahydroisoquinolin-7-yl]pyridazin-3-amine. Also disclosed are pharmaceutical compositions comprising tetrahydroisoquinolines, methods of using tetrahydroisoquinolines in the treatment of depression and other conditions and methods for obtaining the crystalline form. One such intermediate has the following structure:

RELATED APPLICATIONS

This application claims the benefit of U.S. 61/058,717, filed Jun. 4, 2008, now abandoned.

The present disclosure generally relates to processes for preparing tetrahydroisoquinolines, intermediates useful in the preparation of tetrahydroisoquinolines, processes for preparing such intermediates, and a crystalline form of 6-[(4S)-2-methyl-4-(naphthyl)-1,2,3,4-tetrahydroisoquinolin-7-yl]pyridazin-3-amine. The present disclosure also generally relates to pharmaceutical compositions comprising tetrahydroisoquinolines, methods of using tetrahydroisoquinolines in the treatment of depression and other conditions and methods for obtaining the crystalline form.

Major depression (unipolar depression) is a condition of high prevalence and very high global burden. The prevalence of the disease in the US was estimated at over 6% in a twelve month period and 16% over a lifetime (See, Kessler R C, Chiu W G, Demler O, Merikangas K R, Walters E E. Prevalence, severity, and comorbidity of 12-month DSM-IV disorders in the National Comorbidity Survey Replication. Arch. Gen. Psychiatry 2005; 62:617-627). According to the World Health Organization, the impact of the disorder is high with depression being the fourth leading cause of disease burden (See, Ustun J L, Ayuso-Mateos S, Chatterji C, Mathers C, Murray J L. Global burden of depressive disorders in the year 2000. British Journal of Psychiatry 2004; 184:386-392). There are many symptoms associated with major depression. These symptoms generally fall into the two major categories of depressed mood and loss of interest and pleasure (anhedonia).

While the etiological basis of mood disorders is not clear, there are lines of evidence that indicate that the disorders are associated with a heterogeneous dysregulation of monoaminergic systems, i.e. those involving dopamine, norepinephrine and serotonin (See, Garlow S J, Nemeroff C B. The neurochemisty of depressive disorders: clinical studies. Neurobiology of Mental Illness, 2nd Edition 2004; 440-460 (Eds Charney and Nestler)). For instance, abnormalities in levels of serotonin, norepinephrine and dopamine metabolites are commonly reported in depressed patients. Furthermore, the leading pharmacotherapies applied to depression are aimed at monoamine systems, primarily serotonin and norepinephrine.

The response rate of typical antidepressants is reported to be on the order of 65% while remission from the disorder is only about 30% (See, Hirschfeld R M, Montgomery S A, Aguglia E, Amore M, et al. Partial response and nonresponse to antidepressant therapy: current approaches and treatment options. J. Clin. Psychiatry 2002; 63:826-837). The onset of action of drugs for depression is often long, on the order of 4 weeks to response. Accordingly, new drugs for treating depression, as well as other conditions, that improved response rate, remission or onset would represent an important improvement over current therapies. The spectrum of symptom relief is also an important component to efficacy since selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs), while effective on symptoms related to depressed mood, are typically not optimally effective in the areas of motivation and interest in pleasure.

Accordingly, there is a need for increased efficacy over SSRIs and SNRIs. In addition, reduction in the degree of side effects is also desired. For example, addressing decreased libido as well as sleep and gastrointestinal disorders (GI) disorders associated with current anti-depressants would provide substantial benefits to patients.

One strategy that has emerged in antidepressant development is the use of triple reuptake inhibitors (TRUIs), which jointly inhibit reuptake of serotonin, norepinephrine, and dopamine. These compounds have been hypothesized to have a more rapid onset of activity and better efficacy over single or dual reuptake inhibitor antidepressants in part due to the addition of the dopamine component. While the monoamine theory of depression is centered around norepineprine and serotonin, there are data that suggest the involvement of dopamine as well (See, Dunlop B W, Nemeroff C B, The role of dopamine in the pathophysiology of depression, Arch. Gen. Psychiatry 2007; 64:327-337: and Papakostas G I, Fava M, A metaanalysis of clinical trials comparing moclobemide with selective serotonin reuptake inhibitors for the treatment of major depressive disorder; Can. J. Psychiatry 2006; 51:783-790). Motivation, concentration and the ability to experience pleasure are regulated in part through central dopaminergic systems and they are also negatively impacted in depression. Subgroups of depressed patients have also been observed to have decreased cerebrospinal fluid (csf) levels of the dopamine metabolite homovanillic acid, suggesting decreased dopaminergic function in those patients. Over the past several years, a number of studies have demonstrated the benefit of combining drugs that have dopamine transporter (DAT) inhibition properties, like bupropion and methyphenidate, with SSRIs or SNRIs (See, Marshall R D, Liebowitz M R. Paroxetine/bupropion combination treatment for refractory depression. 1996; 16:80-81; Bodkin J A, Lasser, R A, Wines J D Jr, Gardner D M, Baldessarini R J. Combining serotonin reuptake inhibitors and buproprion in partial responders to antidepressant monotherapy. J. Clin. Psychaitry 1997; 58:137-145; Lavretsky H, Kim M D, Kumar A, Reynolds C F, Combined treatment with methylphenidate and citalopram for accelerated response in the elderly: an open trial. J. Clin. Psychiatry. 2003; 64:1410-1414; Trivedi M H, Fava M, Wisniewski S R, Thase M E, Quitkin F, et al. Medication augmentation after the failure of SSRIs for depression. N. Engl. J. Med. 2006; 354:1243-1252).

It is desired to provide drugs that target the DAT, serotonin transporter (SERT), and norepinephrine transporter (NET). Desirably, the drug would provide an optimal ratio of SERT, DAT and NET inhibition. Accordingly, SERT, DAT and NET occupancies are important pharmacological criteria for consideration. In one aspect of the invention, compounds are provided that lead to about 20-60% DAT occupancy while maintaining SERT occupancy greater than about 80%.

It is also desired to provide processes for making tetrahydroisoquinolines, intermediates useful in the preparation of tetrahydroisoquinolines, and processes for preparing such intermediates.

The inventions described herein are presented in various aspects as set for the below.

In accordance with the present disclosure, a particular crystalline form of 6-[(4S)-2-methyl-4-(naphthyl)-1,2,3,4-tetrahydroisoquinolin-7-yl]pyridazin-3-amine is provided that may be useful in treating depression in addition to a variety of other conditions, e.g., anxiety disorders, pain, attention deficit disorder (ADD), smoking cessation and obesity. Also in accordance with the present disclosure, there are provided processes for making tetrahydroisoquinolines, intermediates useful in the preparation of tetrahydroisoquinolines, and processes for preparing such intermediates.

For purposes of clarification, the free base racemate of rac-6-[(4)-2-methyl-4-(naphthyl)-1,2,3,4-tetrahydroisoquinolin-7-yl]pyridazin-3-amine, represented by Formula (I) is referred to herein as Compound (1). The (4S)-enantiomer of Compound 1, represented by Formula (II), is referred to herein, in general (without reference to any specific crystalline foul)), as Compound 2. The crystalline form of Compound 2 in accordance with the present disclosure, also represented by Formula (II), is referred to herein as Form N-1.

It has been found that Form N-1, can be repeatedly crystallized and provide high aqueous solubility and excellent purification capacity, thereby making it a suitable candidate for drug development.

The present disclosure provides Form N-1. Also, the present disclosure provides Form N-1, characterized by the following unit cell parameters:

Cell Dimensions:

a=8.4299(4) Å

b=6.0698(3) Å

c=19.0689(12) Å

alpha=90°

beta=100.169(2)°

gamma=90°

Space group Monoclinic, P2₁

Volume 960.39(9) A³

Z, Calculated density 2, 1.267 g/cm³

wherein measurement of free base crystalline form is at a temperature between about 20° C. to about 25° C. Also, the present disclosure provides Form N-1, characterized by fractional atomic coordinates within the unit cell as listed in Table 3, Atomic Coordinates. Also, the present disclosure provides Form N-1 with characteristic peaks in the powder X-Ray diffraction pattern at values of two theta of 4.6±0.1, 9.4±0.1, 10.6±0.1, 14.1±0.1, 15.4±0.1, 18.2±0.1, 19.5±0.1 at a temperature between about 20° C. and about 25° C., based on a high quality pattern collected with a diffractometer (CuKα) with a spinning capillary with 2θ calibrated with a National Institute of Standards and Technology (NIST) or other suitable standard. Also, the present disclosure provides Form N-1 characterized by a melt with decomposition endotherm with onset typically in the range of 235-245° C. Also, the present disclosure provides substantially pure Form N-1. Also, the present disclosure provides pharmaceutical compositions comprising Form N-1 and a pharmaceutically acceptable carrier or diluent. Also, the present disclosure provides pharmaceutical compositions comprising Form N-1 in combination with one or more additional compounds having anti-depression activity.

The present disclosure provides processes for making tetrahydroisoquinolines. Also, the present disclosure provides intermediates useful in the preparation of the tetrahydroisoquinolines. Also, the present disclosure provides processes for preparing such intermediates.

FIG. 1 illustrates experimental and simulated powdered X-Ray diffraction patterns (CuKαλ=1.54178 Å at T=room temperature) of Form N-1.

FIG. 2 illustrates the differential scanning calorimetry pattern of Form N-1.

FIG. 3 illustrates the Solid State Nuclear Magnetic Resonance (SSNMR) spectrum of Form. N-1.

DEFINITIONS

Stereochemical definitions and conventions used herein generally follow McGraw-Hill Dictionary of Chemical Terms, S. P. Parker, Ed., McGraw-Hill Book Company, New York (1984) and Stereochemistry of Organic Compounds, Eliel, E. and Wilen, S., John Wiley & Sons, Inc., New York (1994). Many organic compounds exist in optically active forms, i.e., they have the ability to rotate the plane of plane-polarized light. In describing an optically active compound, the prefixes D and L or R and S are used to denote the absolute configuration of the molecule about its chiral center(s). The prefixes d and 1 or (+) and (−) are employed to designate the sign of rotation of plane-polarized light by the compound, with (−) or 1 meaning that the compound is levorotatory and (+) or d, meaning the compound, is dextrorotatory. For a given chemical structure, these compounds, called stereoisomers, are identical except that they are mirror images of one another. A specific stereoisomer of a mirror image pair may also be referred to as an enantiomer, and a mixture of such isomers is often called an enantiomeric mixture.

The term “chiral” refers to molecules which have the property of non-superimposability of the mirror image partner, while the term “achiral” refers to molecules which are superimposable on their mirror image partner.

The term “derivative” means a chemically modified compound wherein the modification is considered routine by the ordinary skilled chemist, such as an ester or an amide of an acid, protecting groups, such as a benzyl group for an alcohol or thiol, and tert-butoxycarbonyl group for an amine.

The term “enantiomers” refers to two stereoisomers of a compound which are non-superimposable mirror images of one another.

The term “halogen” as used herein and in the claims is intended to include fluorine, bromine, chlorine and iodine while the term “halide” is intended to include fluoride, bromide, chloride and iodide anion.

The term “patient” includes both human and other mammals.

The term “pharmaceutical composition” means a composition comprising Form N-1 in combination with at least one additional pharmaceutical carrier, i.e., adjuvant, excipient or vehicle, such as diluents, preserving agents, fillers, flow regulating agents, disintegrating agents, wetting agents, emulsifying agents, suspending agents, sweetening agents, flavoring agents, perfuming agents, antibacterial agents, antifungal agents, lubricating agents and dispensing agents, depending on the nature of the mode of administration and dosage forms. Ingredients listed in Remington's Pharmaceutical Sciences, 18th ed., Mack Publishing Company, Easton, Pa. (1999) for example, may be used.

The phrase “pharmaceutically acceptable” is employed herein to refer to those compounds, materials, compositions, and/or dosage forms which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of human beings and animals without excessive toxicity, irritation, allergic response, or other problem or complication commensurate with a reasonable risk/benefit ratio.

The term “pharmaceutically acceptable salt” is intended to include nontoxic salts synthesized from a compound which contains a basic or acidic moiety by conventional chemical methods. Generally, such salts can be prepared by reacting the free acid or base forms of these compounds with a stoichiometric amount of the appropriate base or acid, respectively, in water or in an organic solvent, or in a mixture of the two; generally, nonaqueous media like ether, ethyl acetate, ethanol, isopropanol, or acetonitrile are preferred. Lists of suitable salts are found in Remington's Pharmaceutical Sciences, 18th ed., Mack Publishing Company, Easton, Pa., 1990, p. 1445. Suitable inorganic bases such as alkali and alkaline earth metal bases include The term “polymorph” refers to crystalline forms having the same chemical composition but different spatial arrangements of the molecules, atoms, and/or ions forming the crystal.

The terms “racemic mixture” and “racemate” refer to an equimolar mixture of two enantiomeric species, devoid of optical activity. In addition, as used herein, the teens “racemic mixture” and “racemate” are intended to include equimolar mixtures of two enantiomers.

The term “solvate” means a physical association of a compound of this disclosure with one or more solvent molecules. This physical association includes hydrogen bonding. In certain instances the solvate will be capable of isolation, for example when one or more solvent molecules are incorporated in the crystal lattice of the crystalline solid. “Solvate” encompasses both solution-phase and isolable solvates. Exemplary solvates include hydrates, ethanolates, methanolates, and the like.

The term “stereoisomers” refers to compounds which have identical chemical constitution, but differ with regard to the arrangement of the atoms or groups in space.

The term “substantially pure” refers to chemical purity and form purity. More specifically, substantially pure Form N-1 comprises at least about 95 wt %, preferably at least about 98 wt %, more preferably at least about 99 wt % of Form N-1 and less than about 5 wt %, preferably less than about 2 wt %, and more preferably less than about 1 wt % of other compounds having a different chemical structure than Compound 2. Additionally, substantially pure Form N-1 comprises at least about 95 wt %, preferably at least about 98 wt %, more preferably at least about 99 wt % of Form N-1 and less than about 5 wt %, preferably less than about 2 wt %, and more preferably less than about 1 wt % of any other crystalline form of Compound 2. This means that the Form N-1 preferably contains less than about 5 wt % of other compounds, and less than about 5 wt % of any other form (also referred to as “phase homogenicity”).

The term “therapeutically effective amount” means the total amount of Form N-1 that is sufficient to show a meaningful patient benefit. When applied to an individual active ingredient, administered alone, the term refers to that ingredient alone. When applied to a combination, the term refers to combined amounts of the active ingredients that result in the therapeutic effect, whether administered in combination, serially or simultaneously. If Form N-1 is used in combination with another medication, i.e., drug, the combination of compounds described herein may result in a synergistic combination. Synergy, as described for example by Chou and Talalay, Adv. Enzyme Regul. 1984, 22, 27-55, occurs when the effect of the compounds when administered in combination is greater than the effect of the compounds when administered alone as single agents.

The term “treating” refers to: (i) preventing a disease, disorder or condition from occurring in a patient which may be predisposed to the disease, disorder and/or condition but has not yet been diagnosed as having it; (ii) inhibiting the disease, disorder or condition, i.e., arresting its development; and (iii) relieving the disease, disorder or condition, i.e., causing regression of the disease, disorder and/or condition.

For ease of reference, the following abbreviations when used in this disclosure have the meanings given below:

ACN = acetonitrile; AcOH and HOAc = acetic acid; Boc = t-butoxycarbonyl; CSA = camphorsulfonic acid; DCM = dichloromethane; DMAP = 4-N,N-dimethylaminopyridine; DMF = N,N-dimethylformamide; DIPEA = diisopropylethylamine; DPPA = diphenylphosphoryl azide; DMSO = dimethyl sulfoxide; EtOAc = ethyl acetate; Et₃N = triethylamine; EtOH = ethanol; IPA = isopropanol; IPAc = isopropyl acetate; KOAc = potassium acetate; MeOH = methanol MSA = methanesulfonic acid; MTBE = methyl tert-butyl ether; NBS = N-bromosuccinamide; TFA = trifluoroacetic acid; THF = tetrahydrofuran; g = grams; h = hours; kg = kilograms; L = liters; min = minutes; mL = milliliters; mmol = millimoles; mol = moles;

General Preparation of Crystalline Materials

Crystalline forms may be prepared by a variety of methods, including for example, crystallization or recrystallization from a suitable solvent, sublimation, growth from a melt, solid state transformation from another phase, crystallization from a supercritical fluid, and jet spraying. Techniques for crystallization or recrystallization of crystalline forms from a solvent mixture include, for example, evaporation of the solvent, decreasing the temperature of the solvent mixture, crystal seeding a supersaturated solvent mixture of the molecule and/or salt, freeze drying the solvent mixture, and addition of antisolvents (countersolvents) to the solvent mixture. High throughput crystallization techniques may be employed to prepare crystalline forms including polymorphs. Crystals of drugs, including polymorphs, methods of preparation, and characterization of drug crystals are discussed in Solid-State Chemistry of Drugs, S. R. Byrn, R. R. Pfeiffer, and J. G. Stowell, 2^(nd) Edition, SSCI, West Lafayette, Ind. (1999).

For crystallization techniques that employ solvent, the choice of solvent or solvents is typically dependent upon one or more factors, such as solubility of the compound, crystallization technique, and vapor pressure of the solvent, or the ability to afford a substantially pure crystalline form. Combinations of solvents may be employed, for example, the compound may be solubilized into a first solvent to afford a solution, followed by the addition of an antisolvent to decrease the solubility of the compound in the solution and to afford the formation of crystals. An antisolvent is a solvent in which the compound has low solubility.

In one method to prepare crystals, a compound is suspended and/or stirred in a suitable solvent to afford a slurry, which may be heated to promote complete or partial dissolution. The term “slurry”, as used herein, means a saturated solution of the compound, which may also contain an additional amount of the compound to afford a heterogeneous mixture of the compound and a solvent at a given temperature.

Seed crystals may be added to any crystallization mixture to promote crystallization. Seeding may be employed to control growth of a particular polymorph or to control the particle size distribution of the crystalline product and/or afford a substantially pure crystalline form. Accordingly, calculation of the amount of seeds needed depends on the size of the seed available and the desired size of an average product particle as described, for example, in “Programmed Cooling of Batch Crystallizers,” J. W. Mullin and J. Nyvlt, Chemical Engineering Science, 1971, 26, 369-377. In general, seeds of small size are needed to control effectively the growth of crystals in the batch. Seed of small size may be generated by sieving, milling, or micronizing of large crystals, or by micro-crystallization of solutions. Care should be taken that milling or micronizing of crystals does not result in any change in crystallinity of the desired crystal form (i.e., change to amorphous or to another polymorph).

A cooled crystallization mixture may be filtered under vacuum, and the isolated solids may be washed with a suitable solvent, such as cold recrystallization solvent, and dried under a nitrogen purge to afford the desired crystalline form. The isolated solids may be analyzed by a suitable spectroscopic or analytical technique, such as solid state nuclear magnetic resonance, X-Ray powder diffraction, or the like, to assure formation of the preferred crystalline form of the product. The resulting crystalline form is typically produced in an amount of greater than about 70 weight percent isolated yield, preferably greater than 90 weight percent isolated yield, based on the weight of the compound originally employed in the crystallization procedure. The product may be co-milled or passed through a mesh screen to delump the product, if necessary.

Crystalline forms may be prepared, for example, directly from the reaction medium of the process for preparing Compound 2. This may be achieved, for example, by employing in the final process step a solvent or a mixture of solvents from which Form N-1 may be crystallized. Alternatively, crystalline forms may be obtained by distillation or solvent addition techniques. Suitable solvents for this purpose include, for example, non-polar solvents and polar solvents, including protic polar solvents such as alcohols, and aprotic polar solvents such as ketones, the details and selection of which are known to those skilled in the art.

The presence of more than one polymorph in a sample may be determined by techniques such as powder X-Ray diffraction (PXRD) or solid state nuclear magnetic resonance spectroscopy (SSNMR). For example, the presence of extra peaks in an experimentally measured PXRD pattern when compared with a simulated PXRD pattern may indicate more than one polymorph in the sample. The simulated PXRD may be calculated from single crystal X-Ray data. see Smith, D. K., “A FORTRAN Program for Calculating X-Ray Powder Diffraction Patterns,” Lawrence Radiation Laboratory, Livermore, Calif., UCRL-7196 (April 1963). In one aspect, Form N-1 has phase homogeneity indicated by less than 5 percent, preferably less than 2 percent, and more preferably less than 1 percent of the total peak area in the experimentally measured PXRD pattern arising from the extra peaks that are absent from a simulated PXRD pattern.

Preferably, the crystallization technique provides a product consisting essentially of Form N-1. The crystallized material preferably comprises at least 95 wt % of Form N-1, based on the weight of Compound 2 in the composition. The remaining material may comprise other form(s) of the compound and/or reaction impurities and/or processing impurities arising from its preparation. The presence of reaction impurities and/or processing impurities may be determined by analytical techniques known in the art, such as, for example, chromatography, nuclear magnetic resonance spectroscopy, mass spectrometry, or infrared spectroscopy.

Characterization

Form N-1 can be characterized using various techniques, which are well known to those of ordinary skill in the art. Examples of characterization methods include, but are not limited to, single crystal X-Ray diffraction, powder X-Ray diffraction (PXRD), simulated powder X-Ray patterns (Yin, S.; Scaringe, R. P.; DiMarco, J.; Galena, M. and Gougoutas, J. Z., American Pharmaceutical Review, 2003, 6, 2, 80), differential scanning calorimetry (DSC), solid-state ¹³C NMR (Earl, W. L. and Van der Hart, D. L., J. Magn. Reson., 1982, 48, 35-54), Raman spectroscopy, infrared spectroscopy, moisture sorption isotherms, thermal gravimetric analysis (TGA), and hot stage techniques.

The forms may be characterized and distinguished using single crystal X-Ray diffraction, which is based on unit cell measurements of a single crystal of form N-1. A detailed description of unit cells is provided in Stout & Jensen, X-Ray Structure Determination: A Practical Guide, Macmillan Co., New York (1968), Chapter 3, which is herein incorporated by reference. Alternatively, the unique arrangement of atoms in spatial relation within the crystalline lattice may be characterized according to the observed fractional atomic coordinates. Another means of characterizing the crystalline structure is by powder X-Ray diffraction analysis in which the diffraction profile is compared to a simulated profile representing pure powder material, both run at the same analytical temperature, and measurements for the subject form characterized as a series of 20 values.

One of ordinary skill in the art will appreciate that an X-Ray diffraction pattern may be obtained with a measurement of error that is dependent upon the measurement conditions employed. In particular, it is generally known that intensities in an X-Ray diffraction pattern may fluctuate depending upon measurement conditions employed. It should be further understood that relative intensities may also vary depending upon experimental conditions, and, accordingly, the exact order of intensity should not be taken into account. Additionally, a measurement error of diffraction angle for a conventional X-Ray diffraction pattern is typically about 5 percent or less, and such degree of measurement error should be taken into account as pertaining to the aforementioned diffraction angles. Consequently, it is to be understood that the crystal forms of the present disclosure are not limited to the crystal forms that provide X-Ray diffraction patterns completely identical to the X-Ray diffraction patterns depicted in the accompanying Figures disclosed herein. Any crystal form that provides an X-Ray diffraction pattern, and DSC thermogram substantially identical to those disclosed in the accompanying Figures fall within the scope of the present disclosure. The ability to ascertain substantial identities of X-Ray diffraction patterns is within the purview of one of ordinary skill in the art.

Utility

Certain of the compounds of the disclosure, e.g., Compound 1, Compound 2 or Form N-1, alone or in combination with other compounds, may be used to treat depression. Form N-1, alone or in combination with other compounds, may be used to treat other conditions, such as, for example, neurological conditions, psychiatric conditions and immunological conditions, e.g., anxiety disorders, pain, ADD, smoking cessation and obesity. Form N-1, alone or in combination with other compounds, i.e., drugs, can be used to treat patients afflicted with various conditions (also referred to as “disorders”) by administering to said patients a dose of a pharmaceutical composition provided herein. Examples of disorders that may be treatable by pharmaceutical compositions comprising Form N-1 include, without limitation, ADD, attention deficit disorder hyperactivity disorder (ADHD), cognition impairment, anxiety disorders, especially generalized anxiety disorder (GAD), panic disorder, unipolar depression, also known as major depression, bipolar disorder, also known as manic depression or manic-depressive disorder, obsessive compulsive disorder (OCD), posttraumatic stress disorder (PTSD), acute stress disorder, social phobia, simple phobia, pre-menstrual dysphoric disorder (PMDD), social anxiety disorder (SAD), major depressive disorder (MDD), supranuclear palsy, eating disorders, especially obesity, anorexia nervosa, bulimia nervosa, and binge eating disorder, analgesia (including neuropathic pain, especially diabetic neuropathy), substance abuse disorders (including chemical dependencies) like nicotine addiction, cocaine addiction, alcohol and amphetamine addiction, Lesch-Nyhan syndrome, neurodegenerative diseases like Parkinson's disease, late luteal phase syndrome or narcolepsy, psychiatric symptoms anger such as, rejection sensitivity, movement disorders, like extrapyramidal syndrome, Tic disorders and restless leg syndrome (RLS), tardive dyskinesia, supranuclear palsy, sleep related eating disorder (SRED), night eating syndrome (NES), urinary incontinence (including stress urinary incontinence (SUI) and mixed incontinence), migraine, fibromyalgia syndrome (FS), chronic fatigue syndrome (CFS), sexual dysfunction especially premature ejaculation and male impotence, thermoregulatory disorders (e.g., hot flashes that may be associated with menopause), and lower back pain.

The processes disclosed herein have utility in making tetrahydroisoquinolines, and intermediates useful in the preparation of tetrahydroisoquinolines. The intermediates have utility in making the tetrahydroisoquinolines of the present disclosure, e.g., Compound 1, Compound 2, and Form N-1, as well as other compounds.

The present disclosure also provides pharmaceutical compositions comprising a therapeutically effective amount of Form N-1 and at least one pharmaceutically acceptable carrier.

The active ingredient, i.e., Form N-1 in such compositions typically comprises from 0.1 weight percent to 99.9 percent by weight of the composition, and often comprises from about 5 to 95 weight percent. In some cases, the pH of the formulation may be adjusted with pharmaceutically acceptable modifiers (such as calcium carbonate and magnesium oxide) to enhance the stability of the formulated compound or its delivery form. Formulations of the polymorph of the present disclosure may also contain additives for enhancement of absorption and bioavailability, or to improve the formulation process.

The pharmaceutical compositions of this disclosure may be administered orally (as a solution or solid formulation), parenterally or via an implanted reservoir. The term parenteral as used herein includes subcutaneous, intracutaneous, intravenous, intramuscular, intra-articular, intrasynovial, intrasternal, intrathecal, and intralesional injection or infusion techniques.

The pharmaceutical compositions may be in the form of a sterile injectable preparation, for example, as a sterile injectable aqueous or oleaginous suspension. This suspension may be formulated according to techniques known in the art using suitable dispersing or wetting agents and suspending agents. The details concerning the preparation of such compounds are known to those skilled in the art.

When orally administered, the pharmaceutical compositions of this disclosure may be administered in any orally acceptable dosage form including, but not limited to, capsules, tablets, and aqueous suspensions and solutions. In the case of tablets for oral use, carriers which are commonly used include lactose and corn starch, Lubricating agents, such as magnesium stearate, can also be added. For oral administration in a capsule form, useful carriers/diluents include lactose, high and low molecular weight polyethylene glycol, and dried corn starch. When aqueous suspensions are administered orally, the active ingredient is combined with emulsifying and suspending agents. If desired, certain sweetening and/or flavoring and/or coloring agents may be added.

Other suitable carriers for the above noted compositions can be found in standard pharmaceutical texts, e.g. in “Remington's Pharmaceutical Sciences”, 19th ed., Mack Publishing Company, Easton, Pa., 1995. Further details concerning the design and preparation of suitable delivery forms of the pharmaceutical compositions of the disclosure are known to those skilled in the art.

As the skilled artisan will appreciate, the appropriate dosage of Form N-1 may be determined by a skilled medical practitioner. Specific dosage and treatment regimens for any particular patient will depend upon a variety of factors, including the activity of the specific compound employed, the age, body weight, general health status, gender, diet, time of administration, the duration of treatment, rate of excretion, drug combination, the severity and course of the condition, the patient's disposition to the condition and the judgment of the treating physician.

In one aspect of the invention, there is provided a compound having the following formula:

where R₁ is selected from the group consisting of Br and H₃CO. One such compound has the following formula:

In one aspect of the invention, there is provided a compound having the following formula:

where R₁ is selected from the group consisting of Br and H₃CO. One such compound has the following formula:

In one aspect of the invention, there is provided a compound having the following formula:

where R₂ is selected from the group consisting of Br, H₃CO and HO. One such compound has the following formula:

In one aspect of the invention, there is provided a compound having the following formula:

where R₃ is selected from the group consisting of

where R₄ is C₁-C₄ alky, aryl or phenyl, and n is 1 or 2. One such compound has the following formula:

In one aspect of the invention, there is provided a compound having the following formula:

where each R₅ is independently selected from the group consisting of hydrogen t-butoxycarbonyl, carboxybenzyl, para-methoxybenzylcarbonyl, para-methoxybenzyl, 2,4-dimethoxybenzyl, benzyl, 9-fluorenylmethyloxycarbonyl, N-phthalimide, COCH₃ and COCF₃. Unless otherwise indicated herein, when reference is made to the R₅ substituent on a compound of the disclosure, more typically R₅ will be selected from the group consisting of hydrogen t-butoxycarbonyl, carboxybenzyl, para-methoxybenzylcarbonyl, para-methoxybenzyl and 2,4-dimethoxybenzyl, and even more typically R₅ will be t-butoxycarbonyl. One such compound has the following formula:

In one aspect of the invention, there is provided a compound having the following formula:

where each R₅ is independently selected from the group consisting of hydrogen, t-butoxycarbonyl, carboxybenzyl, para-methoxybenzylcarbonyl, para-methoxybenzyl, 2,4-dimethoxybenzyl, benzyl, 9-fluorenylmethyloxycarbonyl, N-phthalimide, COCH₃ and COCF₃. One such compound has the following formula:

In one aspect of the invention, there is provided a compound having the following formula:

where each R₅ is independently selected from the group consisting of hydrogen, t-butoxycarbonyl, carboxybenzyl, para-methoxybenzylcarbonyl, para-methoxybenzyl, 2,4-dimethoxybenzyl, benzyl, 9-fluorenylmethyloxycarbonyl, N-phthalimide, COCH₃ and COCF₃. One such compound has the following formula:

In one aspect of the invention, there is provided a compound having the following formula:

where each R₅ is independently selected from the group consisting of hydrogen, t-butoxycarbonyl, carboxybenzyl, para-methoxybenzylcarbonyl, para-methoxybenzyl, 2,4-dimethoxybenzyl, benzyl, 9-fluorenylmethyloxycarbonyl, N-phthalimide, COCH₃ and COCF₃, and X is selected from the group consisting of Cl, Br, I and trifluoromethanesulfonyloxy. One such compound has the following formula:

In one aspect of the invention, there is provided a compound having the following formula:

where R⁶ is selected from the group consisting of C₁-C₄ alkyl, benzyl, para-methoxybenzyl, 2,4-dimethoxybenzyl, 3,4-dimethoxybenzyl, and silyl protecting groups such as, but not limited to, tert-butyldimethylsilyl, tert-butyldiphenylsilyl, and triisopropylsilyl. In one such compound, R⁶ is CH₃.

In one aspect of the invention, there is provided a compound having the following formula:

where each R₅ is independently selected from the group consisting of hydrogen, t-butoxycarbonyl, carboxybenzyl, para-methoxybenzylcarbonyl, para-methoxybenzyl, 2,4-dimethoxybenzyl, benzyl, 9-fluorenylmethyloxycarbonyl, N-phthalimide, COCH₃ and COCF₃. One such compound has the following formula:

In one aspect of the invention, there is provided a process for making a compound having the formula:

where R₂ is selected from the group consisting of Br, H₃CO and HO, comprising reacting a compound having the formula:

where R₁ is selected from Br or H₃CO, under conditions effective to promote the formation of Compound 17R.

In one aspect of the invention, there is provided a process for making a compound having the formula:

comprising reacting a compound having the formula:

under conditions effective to promote the formation of compound 6.

In one aspect of the invention, there is provided a process for making a compound having the formula:

comprising reacting a compound having the formula;

where R₂ is selected from the group consisting of Br, H₃CO and HO, under conditions effective to promote the formation of a compound having the formula;

where R₃ is selected from

where R₄ is C₁-C₄ alky, aryl or phenyl, and n is 1 or 2, and reacting Compound 18R under conditions effective to promote the formation of compound rac-1.

In one aspect of the invention, there is provided a process for making a compound having the formula:

comprising reacting a compound having the formula;

under conditions effective to promote the formation of a compound having the formula

and reacting compound 8 under conditions effective to promote the formation of Compound 2.

In one aspect of the invention, there is provided a process for making a compound having the formula:

comprising reacting a compound having the formula;

under conditions effective to promote the formation of Compound 28.

In one aspect of the invention, there is provided a process for making a compound having the formula:

comprising reacting a compound having the formula;

under conditions effective to promote the formation of compound rac-1.

In one aspect of the invention, there is provided a process for making a compound having the formula:

comprising reacting a compound having the formula;

under conditions effective to promote the formation of Compound 29.

In one aspect of the invention, there is provided a process for making a compound having the formula:

comprising reacting a compound having the formula;

under conditions effective to promote the formation of compound rac-1.

In one aspect of the invention, there is provided a process for making a compound having the formula:

comprising reacting a compound having the formula

where each R₅ is independently selected from the group consisting of hydrogen, t-butoxycarbonyl, carboxybenzyl, para-methoxybenzylcarbonyl, para-methoxybenzyl, 2,4-dimethoxybenzyl, benzyl, 9-fluorenylmethyloxycarbonyl, N-phthalimide, COCH₃ and COCF₃, under conditions effective to promote the formation of Compound 2.

In one aspect of the invention, there is provided a process for making a compound having the formula:

comprising reacting a compound having the formula

where R₃ is selected from the group consisting of

where R₄ is C₁-C₄ alky, aryl or phenyl, and n is 1 or 2, under conditions effective to promote the formation of compound rac-1.

In one aspect of the invention, there is provided a process for making a compound having the formula:

where R⁶ is selected from the group consisting of C₁-C₄ alkyl, benzyl, para-methoxybenzyl, 2,4-dimethoxybenzyl, 3,4-dimethoxybenzyl, tert-butyldimethylsilyl, tert-butyldiphenylsilyl, and triisopropylsilyl,

comprising reacting a compound of formula

under conditions effective to promote the formation of compound 7R.

In one aspect of the invention, there is provided a process for making a compound having the formula:

where R⁶ is selected from the group consisting of C₁-C₄ alkyl, benzyl, para-methoxybenzyl, 2,4-dimethoxybenzyl, 3,4-dimethoxybenzyl, tert-butyldimethylsilyl, tert-butyldiphenylsilyl, and triisopropylsilyl,

comprising reacting a compound of formula

under conditions effective to promote the formation of compound 7R.

In one aspect of the invention, there is provided a process for making a compound having the formula:

where R⁶ is selected from the group consisting of C₁-C₄ alkyl, benzyl, para-methoxybenzyl, 2,4-dimethoxybenzyl, 3,4-dimethoxybenzyl, tert-butyldimethylsilyl, tert-butyldiphenylsilyl, and triisopropylsilyl,

comprising reacting a compound of formula

under conditions effective to promote the formation of Compound 22R.

The compounds of the present disclosure, as well as the intermediates disclosed, may be prepared, for example, by the processes described in the following reaction Schemes. Exemplary reagents and procedures for these reactions appear hereinafter or are described above. Starting materials are commercially available or can be readily prepared by one of ordinary skill in the art. The conditions effective to promote the formation of the desired compounds, e.g., solvents, reagents, acids, salts, protecting groups, techniques, catalysts, pressures, temperatures, reaction times, and the like, can be readily determined those skilled in the art. The following are non-limiting examples of reaction schemes that can be used to prepare compounds of the disclosure, including without limitation Compound 2 and Form N-1. Representative synthesis schemes are illustrated below.

Preparation of Compound 2

The synthesis of Compound 2 can utilize a general approach for C-7 and C-4 substituted tetrahydroisoquinolines. A functional handle at C-7, allows the installation of the heterocycle using a palladium-catalyzed Suzuki coupling and the aryl substitutent at C-4 is incorporated from commercially available starting materials.

A preferred synthesis begins with the reductive amination of commercially available m-anisealdehyde using methyl amine and sodium bororhydride in an appropriate solvent such as a mixture of methanol and water to afford Compound 3 in quantitative yield (Synthesis Scheme 1). In this example the methoxy group will be the functional handle for installation of the C-7 pyridazine heterocycle. Alternatively m-bromobenzaldehyde has been demonstrated to be a suitable starting material (Synthesis Scheme 2). In this example bromine is the functional handle. A number of alternative reducing agents can be envisioned to install the amine functionality Alkylation of the secondary amine with α-bromo-2′-acetonapthone and an appropriate base composed of either an organic amine bases such as triethylamine or an inorganic base, afforded ketone Compound 4. Dichloromethane is the preferred solvent, although a number of solvents can be used including EtOAc, IPAc, MTBE, MeOH, EtOH, THF, ACN. Immediate reduction of the resulting ketone with sodium borohydride afforded Compound 5 which was subsequently cyclized under acidic Friedel-Crafts conditions to afford racemic tetrahydroisoquinoline Compound 6 and its regioisomer in approximately 2.5:1 ratio. A number of acids can be envisioned including protic acids such as methanesulfonic acid and sulfuric acid and Lewis acids such as TiCl₄ and AlCl₃. The regioisomers are separated via the oxlate salts and then a selective crystallization in ethanol. The oxalate salt of the desired isomer is then converted to the free base by treatment with aqueous sodium hydroxide and subsequently isolated by extraction with MTBE. A second iteration of this procedure improves the ratio to >97:3. Classical resolution of the desired enantiomer, Compound 7, is achieved using di-p-toluoyl-D-tartaric acid. The desired tartrate salt is more insoluble in acetone, and isolated by filtration. After treatment with aqueous sodium hydroxide to afford the free base, the first pass affords a 95:5 mixture of enantiomers. A second iteration provides >99% ee with chemical purity>99%. Alternatively the mixture of stereo- and regioisomers could be purified by chiral chromatography. Demethylation of Compound 7 with hydrobromic acid in acetic acid affords the phenol hydrobromide salt, Compound 8, which is converted directly to the triflate, Compound 9, by using two equivalents of an organic amine base, such as triethylamine, DIPEA or pyridine, and trifluoromethanesulfonic anhydride in dichlorormethane. Alternatively the freebase of Compound 8 can be used successfully in the subsequent Suzuki coupling. A number of combinations of solvent, boronate, catalyst and ligands can be envisioned for the subsequent Suzuki coupling. In this example, the crude triflate was converted to the crude boronate ester Compound 10 using bis(pinacolato)diboron, KOAc and PdCl₂(dppf) in DMSO. Subsequent Suzuki coupling directly with 3-amino-6-chloropyridazine using PdCl₂(dppf), Cs₂CO₃ in a DMF/water mixture afforded the desired Compound 2 directly but required a tedious workup and laborious purification to afford pure product. Alternatively, using N,N,-di-tert-butoxycarbonyl (Boc) protected 3-amino-6-chloropyridazine (Compound 11) in the Suzuki coupling under similar conditions in a mixture of DMSO and water afford Compound 12. Compound 11 is readily prepared from commercially available 3-amino-6-chloropyridazine, di-tert-butyl dicarbonate, and DMAP in DMF. Recrystallization of the bis-protected product from IPA/water significantly reduces the mono-boc amino pyridazine intermediate. Work-up of the crude reaction mixture of Compound 12 with aqueous LiCl, aqueous NH₄OH, or treatment with a suitable metal scavengers such as Si-Thiol (Silicycle®), or activated carbon, or recrystallization from alcoholic solvent such as methanol are effective means in reducing the metal contamination of the desired product. The Boc protecting groups are removed under acidic conditions using HCl in an alcoholic solvent, such as methanol or isopropanol to afford the di-HCl salt, Compound 13. The free base, Compound 2, is produced by crystallization from a mixture of aqueous sodium bicarbonate and methanol.

Alternatively on preparative scale: 3-amino-6-chloropyridazine can be be coupled under Suzuki conditions with Compound 18, to afford racemic Compound 1 (Synthesis Scheme 2). Compound 17, is readily accessible using similar procedures as discussed above and shown in Synthesis Scheme 1, but starting with m-bromobenzaldehyde, where the C-7 bromine atom is the functional handle for installing the heterocycle. Separation of the desired (4S) enantiomer can be carried out on preparative scale using chiral HPLC on a CHIRALCEL OD column. Subsequent treatment of Compound 2 with L-tartaric acid in MeOH generated the L-tartrate salt, in quantitative yield.

Confirmation of Absolute Configuration of Compound 2 Via Asymmetric Synthesis of Compound 7

Proof of the absolute configuration of Compound 2 was achieved by executing an asymmetric synthesis of Compound 7 and X-ray analysis of intermediate Compound 22. (Synthesis Scheme 3). The asymmetric synthesis began with NBS-bromination of m-anisaldehyde to give Compound 19 in 87% yield. The ketal Compound 20 was prepared from Compound 19 using ethylene glycol with camphorsulfonic acid as catalyst in quantitative yield. Heck coupling of Compound 20 with (R)-3-acryloyl-4-phenyloxazolidin-2-one using tri-o-tolyl phosphine and palladium acetate gave Compound 21 in 81% yield. Grignard addition of the complex formed by 2-naphthyl magnesium bromide and copper(I) bromide-dimethyl sulfide to a solution of Compound 21 at −78° C., with warming to room temperature, produced Compound 22 in 85% yield, with a d.e. of approximately 98%. The absolute configuration of Compound 22 was confirmed by single crystal X-ray crystallography (see structure below). The chiral auxiliary was cleaved by saponification to give carboxylic acid Compound 23, which was converted with DPPA and MeOH to the methyl carbamate Compound 24 in 59% yield. The ketal of Compound 24 was cleaved at 0° C. with HCI. After isolation of the intermediate aldehyde, ring closure under reductive amination conditions gave Compound 25 in 60% yield. Reduction of the carbamate group using LiAlH₄ provided Compound 7 in 70% yield. This compound co-eluted by chiral LC with authentic material prepared by the earlier methods.

Convergent Synthesis of Compound rac-1

A more convergent approach to Compound rac-1 is shown in Synthesis Scheme 4. Suzuki coupling of 3-formylphenylboronic acid and Compound 11 afforded Compound 26 in 95% yield. Reductive amination of Compound 26 with methylamine and sodium bororhydride in an appropriate solvent such as a mixture of methanol and water afforded Compound 27. Alkylation of Compound 27 with alpha bromo-2′-acetonaphtone, followed by reduction of the ketone afforded Compound 29 in 60% yield over three steps. Alternatively, Compound 29 can be accessed in a more direct fashion by reductive amination of Compound 26 with Compound 30. Compound 30 is accessed by amination of alpha bromo-2′-acetonaphtone using hexamethylenetetramine (HMTA) followed by refluxing concentrated HCl (aq) in methanol to afford the primary amine. Treating the primary with ethyl chloroformate, followed by lithium aluminum hyride afforded Compound 30. 2-(2-naphthalenyl)-oxirane is also a proposed logical synthon for alkylation of Compound 27, that would afford direct access to Compound 29. Alternatively, treating alpha bromo-2′-acetonaphthone successively with methylamine and NaBH4 also affords Compound 30. It is envisioned that cyclization of Compound 29 under acidic Friedel-Crafts conditions will afford Compound rac-1 with high region selectivity due to the C7 appended heterocycle. A number of acids can be envisioned including protic acids such as methanesulfonic acid and sulfuric acid and Lewis acids such as TiCl₄ and AlCl₃.

Furthermore, Compound 2 can also be prepared as depicted in Synthesis Scheme 5. Compound 10 reacts with 3,6-dichloropyridazine under Suzuki conditions to give Compound 31 which can then be converted to Compound 32 by reacting with 2,4-dimethoxybenzylamine. Removing of the 2,4-dimethoxybenzyl group on compound 31 by the treatment with trifluoroacetic acid afforded Compound 2. Compound 2 can be further converted to the corresponding maleic acid salt.

EXAMPLES

The following examples are provided for illustrative purposes and are not intended to limit the scope of the claimed invention.

Preparation of 1-(3-methoxyphenyl)-N-methylmethanamine (Compound 3)

To a solution of m-anisaldehyde (205 g, 1.5 mol) in methanol (800 mL) at room temperature was added methylamine (130 mL of 40% in water, 1.5 mol). The resulting solution was cooled to 0° C. and sodium borohydride (83 g, 2.3 mol) was added in batches. The reaction solution was stirred at 0° C. for 2 h, then warmed to room temperature, concentrated in vacuo and diluted with water. The organic phase was separated, diluted with ethyl acetate, washed with 1:1 water/brine, dried over sodium sulfate and concentrated in vacuo to give the desired benzylamine (158.5 g, 70%) as a clear oil. The combined aqueous extracts were extracted with dichloromethane (3×). The combined methylene chloride extracts were washed with 1:1 water/brine, dried over sodium sulfate and concentrated in vacuo to give additional benzylamine (66.7 g, 29%) as a clear oil: ¹H NMR (300 MHz, CDCl₃) δ 7.24 (t, J=8.4 Hz, 1H), 6.91-6.78 (m, 3H), 3.81 (s, 3H), 3.73 (s, 2H), 2.46 (s, 3H),

Preparation of 2-((3-methoxybenzyl)(methyl)amino)-1-(naphthalen-2-yl)ethanone (Compound 4)

To a solution of α-bromo-2′-acetonaphthone (386.2 g, 1.57 mol) in dichloromethane (2.5 L) at 0° C. was added Compound 3 (249.1 g, 1.65 mol) in 30 min, followed by the addition of triethylamine (220.7 mL, 1.57 mmol) in 45 min. After stirring at 0° C. for 40 min, the reaction mixture was warmed to room temperature and stirred overnight. The reaction solution was then washed with water (2×) and the aqueous layer was re-extracted with dichloromethane (2×). The combined organic extract was dried over sodium sulfate and concentrated in vacuo. The ketone, Compound 4, was obtained as a reddish oil (513.3 g, quantitative), was used in the next step without further purification: ¹H NMR (CDCl₃, 500 MHz) δ 8.50 (s, 1H), 8.01 (d, J=8.5 Hz, 1H), 7.92 (d, 8.0 Hz, 1H), 7.88-7.85 (m, 2H), 7.60-7.54 (m, 2H), 7.26-7.23 (m, 1H), 6.97-6.94 (m, 2H), 6.82 (dd, J=8.0, 2.5 Hz, 1H), 3.88 (s, 2H), 3.75 (s, 3H), 3.69 (s, 2H), 2.42 (s, 3H); ESI MS m/z 320 [M+H]⁺.

Preparation of 2-((3-methoxybenzyl)(methyl)amino)-1-(naphthalen-2-yl)ethanol (Compound 5)

A solution of the ketone, Compound 4, (512.2 g, 1.57 mol) in methanol (4.0 L) was split equally into two flasks. To each half of the ice-cold solution was added sodium borohydride (33.0 g, 0.87 mol) in batches (˜30 min). After the addition, the reaction solution was stirred at 0° C. (internal temperature 10-15° C.) for 50 min before it was quenched slowly with water (˜500 mL). The reaction mixture was then concentrated in vacuo to remove most of the organic solvent. The residue obtained from the two batches were combined, extracted with dichloromethane (2×), dried over sodium sulfate and concentrated in vacuo. The alcohol, Compound 5, was obtained as a yellow oil (510.4 g, quantitative), and was used in the next step without further purification: ¹H NMR (500 MHz, CDCl₃) δ 7.84-7.80 (m, 4H), 7.47-7.44 (m, 3H), 7.27-7.24 (m, 1H), 6.92-6.83 (m, 3H), 4.92 (dd, J=10.0, 4.0 Hz, 1H), 4.14 (br s, 1H), 3.81 (s, 3H), 3.74 (d, J=13.0 Hz, 1H), 3.53 (d, J=13.0 Hz, 1H), 2.68-2.60 (m, 2H), 2.36 (s, 3H); ESI MS m/z 322 [M+H]⁺.

Preparation of racemic 7-methoxy-2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinoline (Compound 6)

A solution of the alcohol, Compound 5, (495 g, 1.54 mol) in dichloromethane (6.0 L) was split equally into two flasks. To each half of the ice-cold solution was added methanesulfonic acid (500 mL, 7.7 mmol) via additional funnel (˜1 h). The reaction solution was allowed to slowly warm to room temperature and stirred for 6-8 h before it was cooled to <10° C. and quenched slowly with an aqueous solution of sodium hydroxide (330 g, 8.3 mol in 600 mL of water). The internal temperature during the addition was kept less than 30° C. The organic layer was then separated, washed with water, dried over sodium sulfate and concentrated in vacuo. The crude product from the two batches were combined and purified by flash column chromatography (hexanes/ethyl acetate 88:12 to ethyl acetate/methanol 99.9:0.1) to give Compound 6 (280.4 g, 60% over 4 steps) as a thick oil: ¹H NMR (500 MHz, CDCl₃) δ 7.81-7.74 (m, 3H), 7.68 (s, 1H), 7.47-7.42 (m, 2H), 7.28-7.26 (m, 1H), 6.79 (d, J=8.5 Hz, 1H), 6.80-6.62 (m, 2H), 4.40 (dd, J=8.5, 6.0 Hz, 1H), 3.80-3.78 (m, 1H), 3.77 (s, 3H), 3.65 (d, J=15.0 Hz, 1H), 3.11-3.08 (m, 1H), 2.65 (dd, J=11.5, 6.0 Hz, 1H), 2.45 (s, 3H); ESI MS m/z 304 [M+H]⁺.

Preparation of racemic 7-methoxy-2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinoline (Compound 6)

Alternatively, the regioisomers can be separated as their respective oxalate salts. A 2.4:1 mixture of regio isomers [547 g, 1.8 mol] in absolute EtOH (2 L) was stirred at ambient temperature as a solution of oxalic acid (162 g, 1.8 mol) in absolute EtOH (600 mL) was added in one portion (exothermic). The solution became heterogeneous, and after 2 h was filtered to give a light yellow solid that was ˜90:10 mixture of regio isomers by ¹H NMR. The filter cake was added to fresh absolute EtOH (6.5 L) and the resulting slurry was heated to 75° C. for 3 hours. The slurry was then cooled to 25° C. and filtered. The filter cake was conditioned under N₂ overnight and then added to satd. NaHCO₃ (3 L). The product was extracted with EtOAc (3.5 L), and the organic layer was dried (MgSO₄) and concentrated to give 355 g of a white solid that was a 96:4 mixture of Compound 6 and its regio isomer in 91% yield and 98.4% purity. ¹H NMR (400 MHz, CDCl₃) δ 7.75 (m, 4H), 7.44 (m, 2H), 7.27 (dd, J=8.4, 1.7 Hz, 1H), 6.70 (m, 3H), 4.39 (m, 1H), 3.77 (m, 4H), 3.63 (m, 1H), 3.08 (ddd, J=11.5, 4.3, 1.2 Hz, 1H), 2.64 (dd, J=11.5, 8.9 Hz, 1H), 2.44 (s, 3H).

Preparation of (S)-7-methoxy-2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinoline (Compound 7)

To a solution of Compound 6 (222.3 g, 0.73 mol) in ethanol (5.5 L) at room temperature was quickly added a solution of di-p-toluoyl-D-tartaric acid (292.2 g, 0.73 mol) in ethanol (1.0 L) with no internal temperature increase noted. The reaction solution was stirred at room temperature. Precipitate started to form within 10 min. After stirring for 2 h, the reaction slurry was filtered and the cake was dried at 60° C. in vacuo for 12 h to give the (4S)-enriched tartrate salt [265.0 g, 52%, with a ratio of enantiomers of approximately 84:16 (Chiralpak AD, heptane:IPA:diethylamine 90:10:0.01)]. The filtrate was concentrated in vacuo and dried at 60° C. to give the 4R-enriched tartrate salt (238.0 g, 47%, ratio of enantiomers of approximately 3:97). The desired 4S enriched tartrate salt was treated with aqueous sodium hydroxide and separated by preparative chiral chromatography to give pure Compound 7. (Preparative chiral chromatography was carried out in two batches of enriched racemate, 117 g and 93 g, respectively. The following conditions were used for the 117 g batch: Thar 350 SFC; Column: Chiralpak AD-H, 5×25 cm; Mobile phase: 30% IPA+0.05% DEA/CO₂; Pressure: 100 bar; Temperature: 45° C.; Flow rate: 240 g/min; Solution concentration ˜250 mg/ml; Injection amount: 8 mL; Cycle time: 10.5 min/inj; Detector: 254 nM; Throughput: 11-12 g/hr. The sample was dissolved in warm 275 mL MeOH and 95 mL IPA with 0.5 mL DEA added).

Alternative Preparation of (S)-7-methoxy-2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinoline (Compound 7)

A solution of racemic Compound 6 (1.2 kg, 1.0 equiv, 97:3 mixture of regioisomers by 1H NMR in acetone was heated to 55° C. in a 100-L jacketed reactor. Simultaneously, a solution of di-p-toluoyl-D-tartaric acid (1.1 kg, 0.80 equiv) in acetone was prepared in a 20-L carboy. A portion of the chiral acid solution (0.45 equiv) was added to the racemic solution over 2 h, causing the solution to become cloudy. Previously prepared seed crystals (10 g, 99% ee) were then added. The mixture continued stirring for an additional 30 min. The remaining chiral acid solution was slowly added over 3 h. The batch was cooled to −5 to 5° C. over 5 h and held at that temperature for 14 h. The slurry was then filtered and the filter cake was conditioned for 6 h under a nitrogen atmosphere. The dried filter cake was then broken into a powder and added to 2 M aqueous NaOH in a clean 50-L reactor. MTBE was added and the biphasic mixture was vigorously stirred for 45 min. The phases were separated and the organic layer was concentrated to give 475 g of an off-white solid (80% yield of (+)-enantiomer, 91:9 enantiomeric ratio). The solid obtained underwent a second iteration of the process described above with only two minor changes: the stoichiometry of the resolving agent was increased from 0.80 equiv to 0.85 equiv and the volume of acetone was increased by 25% in the initial solution. When 450 g of enantio-enriched material (91:9) was used, 370 g of enantiopure Compound 7 was obtained (97% yield based on chiral acid, >99% cc). ¹H NMR (300 MHz, CDCl3) δ 7.72-7.82 (m, 3H), 7.68 (s, 1H), 7.39-7.49 (m, 2H), 7.24 (dd, J=8.5, 1.7 Hz, 1H), 6.76 (d, J=9.4 Hz, 1H), 5.59-6.67 (m, 2H), 4.39 (dd, J=8.9, 5.9 Hz, 1H), 3.82 (d, J=15.0 Hz, 1H), 3.76 (s, 3H), 3.67 (d, J=15.0 Hz), 3.11 (ddd, J=11.5, 5.7, 1.1 Hz, 1H), 2.66 (dd, J=11.6, 9.3 Hz, 1H), 2.45 (s, 3H).

Preparation of (S)-2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinolin-7-ol (Compound 8, free base)

To a solution of Compound 7 (42.5 g, 140 mmol) in 48% HBr (200 mL) was added AcOH (100 mL) to give a light yellow suspension. The reaction was heated to give a light yellow solution and stirred at 120° C. for 6 hr (<1.5% starting material left by HPLC), then concentrated. Dichloromethane (500 mL) was added to the residue and the suspension was filtered. The filtrate was neutralized with ice water, 50% NaOH (added slowly) and Na₂CO₃ solution to pH of 10. The aqueous layer was extracted with dichloromethane twice. The solid was fully dissolved in dichloromethane and triethylamine (25 mL), and washed with Na₂CO₃ solution to pH of 10. The organic layers were combined and washed with NaHCO₃ and brine, dried over Na₂SO₄ overnight, filtered and concentrated. The crude product Compound 8, as the free base, can be used in the next step without further purification.

Preparation of (S)-2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinolin-7-ol (Compound 8, free base)

Alternative procedure: To a solution of Compound 7 (30.0 g, 99.0 mmol) in acetic acid (150 mL) was added hydrobromic acid (48% solution in water, 450 mL). The reaction solution was flushed with nitrogen and heated at 110° C. (internal temperature) for 3 h, at which time HPLC and MS showed no starting material left. The reaction solution was then cooled to room temperature and concentrated in vacuo. The residue obtained was dissolved in methylene chloride and water, then carefully neutralized with saturated aqueous sodium bicarbonate and sodium hydroxide to pH>8. The organic extract was separated, washed with water and brine, dried over sodium sulfate and concentrated in vacuo to give Compound 8 as the freebase, (29.1 g, quantitative yield) as a light yellow solid. The crude product was used in the next step without further purifications: ¹H NMR (500 MHz, CDCl₃) δ 7.81-7.74 (m, 3H), 7.67 (s, 1H), 7.47-7.42 (m, 2H), 7.30-7.25 (m, 1H), 6.73 (d, J=8.5 Hz, 1H), 6.57-6.52 (m, 2H), 4.38 (dd, J=8.5, 6.0 Hz, 1H), 3.73 (d, J=15.0 Hz, 1H), 3.60 (d, J=15.0 Hz, 1H), 3.11-3.08 (m, 1H), 2.63 (dd, J=11.5, 9.5 Hz, 1H), 2.44 (s, 3H); ESI MS m/z 290 [M+H]⁺.

Preparation of (S)-2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinolin-7-ol (Compound 8, HBr salt)

Alternatively, the intermediate HBr salt of Compound 8 can be isolated and used directly in the next step.

Scaled-up procedure: A mixture of Compound 7 (1.0 kg, 1.0 equiv,) in AcOH (2.5 L) was mechanically stirred and heated at 55-60° C. until the solution was homogeneous. 48 wt % HBr in water (5.0 L) was then added in one portion, and the resulting solution was heated to 105° C. for 18 h (the solution became heterogeneous shortly after adding the HBr solution, but became homogeneous after stirring approximately 2 h at 105° C.). The solution was then cooled to 95° C. over 15 minutes. DI water (900 mL) was added over 15 min, and then seeds of authentic Compound 26 (5.0 g) were added. An additional 3.1 L of DI water was then added over 2 hours. The slurry was cooled to 25° C. over 2.5 hours and filtered. The filter cake was conditioned under nitrogen overnight and then added to DI water (4.0 L). The slurry was stirred at ambient temperature for 45 minutes, cooled to 5° C., filtered, conditioned under N₂ overnight, and then dried in vacuo to constant weight to give 1.0 kg of compound 8, HBr salt as a white solid in 85% yield and >99% purity. ¹H NMR (500 MHz, d-DMSO) δ ¹H NMR (500 MHz, d-DMSO) δ 10.31 (s, 0.85H), 10.11 (br s, 0.15H), 9.60 (s, 1H), 7.91 (m, 4H), 7.54 (m, 2H), 7.30 (d, J=7.5 Hz, 1H), 6.67 (s, 1H), 6.61 (m, 2H), 4.64 (m, 1H), 4.54 (br s, 2H), 3.84 (br s, 1H), 3.62 (t, J=11.2 Hz, 1H), 2.98 (s, 3H).

Preparation of (S)-2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinolin-7-yl trifluoromethanesulfonate (Compound 9)

To a solution of Compound 8, free base (28.9 g, 99.0 mmol) in dichloromethane (820 mL) was added pyridine (10.4 mL, 128.7 mmol). The reaction suspension was stirred for 5 min at room temperature to give a solution. The reaction solution was cooled to 0° C. and trifluoromethanesulfonic anhydride (18.5 mL, 108.9 mmol) was added slowly (˜35 min). The reaction mixture was stirred at 0° C. for 45 min before it was quenched with aqueous sodium bicarbonate and extracted with dichloromethane. The combined organic extract was dried over sodium sulfate, filtered and concentrated in vacuo. Compound 9, obtained as a yellow oil, was used in the next step without further purification. ¹H NMR (500 MHz, CDCl₃) δ 7.83-7.70 (m, 3H), 7.67 (s, 1H), 7.49-7.44 (m, 2H), 7.30-7.23 (m, 1H), 7.04 (d, J=2.05 Hz, 1H), 6.98-6.95 (m, 2H),), 4.22 (dd, J=8.0, 6.0 Hz, 1H), 3.81 (dd, J=15.0 Hz, 1H), 3.68 (dd, J=15.0 Hz, 1H), 3.11 (dd, J=11.0, 6.0 Hz, 1H), 2.69 (dd, J=11.0, 3.5 Hz, 1H), 2.46 (s, 3H); ESI MS m/z 422 [M+H]⁺.

Preparation of (S)-2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinolin-7-yl trifluoromethanesulfonate (Compound 9)

Alternative procedure: To a solution of Compound 8, HBr salt (40.5 g, 140 mmol) in DCM (1.2 L) was added diisopropylethylamine (48.9 mL, 280 mmol) to give an orange solution. The reaction was cooled to −50° C. Triflic anhydride (Tf₂O) (35 mL, 207 mmol) was added in portions until no starting material was left. The reaction was monitored by HPLC in 5 min after each portion of Tf₂O addition. When the reaction was finished, aqueous NaHCO₃ solution (600 mL) was added. The organic layer was washed with NH₄Cl solution (500 mL) and brine (500 mL). The combined organic layer was dried over Na₂SO₄, filtered and concentrated. DMSO (500 mL) was added and the residual DCM was removed under reduced pressure to give crude product Compound 9, which was used directly as is and continued in the example below. HPLC (YMC Pack Pro C18 4.6×50, 4 min): Peak at Tr=2.86 min is starting material. Peak at Tr=3.71 min is product.

Note: A test reaction indicated that the use of an excessive amount of Tf₂O may lead to demethylation and other undesired side reactions.

Preparation of (S)-2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinolin-7-yl trifluoromethanesulfonate (Compound 9)

Scaled-up procedure: A mixture of Compound 8 HBr salt (1.0 kg, 1.0 equiv.) in DCM (12.4 L) was stirred at room temperature as Et₃N (0.90 L, 2.3 equiv) was added over 5 minutes (slightly exothermic). After stirring 20 minutes, the solution was homogeneous. The reactor was then cooled to −55 to −60° C. in a dry ice/IPA bath, and Tf₂O (0.56 L, 1.2 equiv.) was added over 2.5 hours, maintaining an internal temperature of <−50° C. After the addition was complete, the mixture was stirred for 20 minutes at −50° C. and HPLC analysis indicated the reaction was complete. The solution was warmed to −10° C. and 10% aq. NaHCO₃ (6.2 L) was added in one portion. The resulting mixture was then warmed to 20° C. and stirred for 30 minutes. The layers were then separated, and the organic phase was washed with DI water (6.2 L) and concentrated under reduced pressure to give 1.2 kg of the crude product Compound 9 as a dark red oil in >100% yield due to residual DCM, but with 73.5% purity.

Preparation of di-tert-butyl (6-chloropyridazin-3-yl)imidodicarbonate (Compound 11)

To a solution of 6-chloropyridazin-3-amine (75 g, 579 mmol) in DMF (600 ml) was added di-tert-butyl dicarbonate (278 g, 1274 mmol) and DMAP (0.6 g, 4.91 mmol) to give a suspension. The mixture was heated to 50° C. to give an orange solution and the reaction temperature reached 75° C. by itself with gas bubbles generated. The heating mantel was removed and the reaction was cooled to 55° C. slowly. Then the reaction was stirred at 55° C. with heating for 2 h to give a dark brown solution. After the reaction was cooled to room temperature, the reaction solution was poured to a 4 L beaker and water (3 L) was added to give a light brown suspension. The yellow precipitate was collected by filtration and washed with water (4 L). No product was dissolved in water. The solid was dried in oven overnight to give product (152.2 g, 80% yield) as a light yellow solid.

Preparation of di-tert-butyl (6-chloropyridazin-3-yl)imidodicarbonate (Compound 11)

Scaled-up procedure: A mixture of 3-chloro-6-aminopyridazine (500 g, 1.0 equiv) and DMAP (3.77 g, 0.008 equiv) in DMF (3.5 L) was heated and stirred at 55° C. for 20 minutes, until the mixture became homogeneous. A solution of Boc₂O (2.2 equiv) in DMF (500 mL) was prepared separately and then added in one portion to the batch, causing an endothermic event. The reaction solution was monitored by HPLC while stirring at 55° C., and after 5 h, the reaction was deemed complete. The solution was cooled to room temperature and then slowly poured into DI water (4.4 L), causing precipitation. The mixture was stirred for 10 minutes and then filtered. The resulting brown solid was conditioned overnight under nitrogen. A mixture of the crude product in 2-propanol (3.5 L) was heated and stirred at 65° C. until the mixture became homogeneous. DI water (3.5 L) was then added over 30 min (temperature was not controlled). The reaction mixture was cooled to room temperature and then filtered to give 805 g Compound 11 as a light brown solid in 63% yield, and 99.7% purity. ¹H NMR (300 MHz, d-DMSO) δ 8.00 (q, J=9.0 Hz, 2H), 1.40 (s, 18H).

Preparation of (5)-di-tert-butyl-(6-(2-methyl-4-(2-naphthyl)-1,2,3,4-tetrahydro-7-isoquinolinyl)-3-pyridazinyl)imidodicarbonate (Compound 12)

(Continued from example above: To the solution of crude Compound 9 (˜140 mmol) (prepared above) in DMSO (800 mL) in a 5 L three-necked round bottom flask was added bis(pinacolato)diboron (42.7 g, 168 mmol) and potassium acetate (41.2 g, 420 mmol). The mixture was stirred at room temperature under nitrogen for 5 min followed by the addition of dichloro[1,1′-ferrocenylbis(diphenyl-phosphine)]palladium(II) dichloromethane (Pd(dppf)Cl₂.CH₂Cl₂) (18.29 g, 22.40 mmol). The reaction was stirred at 80° C. for 0.5 h. HPLC showed no starting material remaining. HPLC (YMC Pack Pro C18 4.6×50, 4 min): Peak at Tr=3.73 min is starting material. Peaks at Tr=3.85 and 2.93 min are the product Compound 10 (LCMS=400.31 [M+H]) and boronic acid (LCMS=318.28 [M+H]), respectively.

To the solution of Compound 10 prepared above was added Compound 11 (175 mmol), Pd(dppf)Cl₂.CH₂Cl₂ (18.29 g, 22.4 mmol), DMSO (400 mL), Cs₂CO₃ (137 g, 420 mmol) and water (250 mL) at 80° C. The reaction was stirred at 80° C. for 2 h.

The reaction was cooled to room temperature and diluted with water (6 L). The black precipitate was collected by filtration, dissolved in DCM (1 L), and washed with 10% LiCl aqueous solution (500 mL). The aqueous layer was back extracted with DCM (400 mL). The combined organic layers were filtered through a Celite pad and concentrated. Crude product Compound 12 was obtained as a dark grey solid (57.4 g, 71% yield, 98% purity) by crystallization in MeOH (300 ml). HPLC (YMC Pack Pro C18 4.6×50, 4 min): Peak at Tr=3.80 is the product Compound 12. LCMS=567.33 [M+H].

Purification of (S)—N,N-di-tert-butyl-(6-(2-methyl-4-(2-naphthyl)-1,2,3,4-tetrahydro-7-isoquinolinyl)-3-pyridazinyl)imidodicarbonate (Compound 12)

1. Several batches was combined together for purification. To a solution of crude Compound 12 (120 g, 98% purity, dark grey solid) in dichloromethane (1 L) was added activated carbon (50 g). The suspension was refluxed for 1 h and the charcoal was filtered off through a Celite pad. The filtrate was concentrated and the residue was recrystallized in MeOH (1 L, reflux 30 min). The solution was cooled to room temperature and the grey crystals were collected by filtration. The recrystallization was repeated two times.

2. The solid was de-colored with charcoal in dichloromethane and recrystallized in MeOH again to give a beige solid.

3. The solid was dissolved in dichloromethane (1 L) and washed with ammonium hydroxide solution (100 ml concentrated NH₄OH+900 ml water) to primarily remove residual iron. The middle black suspension layer between the aqueous layer and dichloromethane layer was removed with the use of a separation funnel. The light yellow dichloromethane layer was dried over Na₂SO₄ and concentrated. The residue was recrystallized in MeOH (500 ml) again to give off-white color solid.

4. The solid was dissolved in dichloromethane (500 ml) and the solution was concentrated. The residue was recrystallized in MeOH (500 ml) and the product was collected by filtration as a white solid. First fraction, 95 g, >99% purity, white solid; second fraction, 10 g, 98% purity from last MeOH mother liquid; third fraction, 1 g, 90% purity from former mother liquid. ¹H NMR (500 MHz, CDCl₃) δ 7.96 (s, 1H), 7.66-7.89 (m, 6H), 7.40-7.53 (m, 3H), 7.28 (d, J=7.15 Hz, 1H), 7.04 (d, J=8.25 Hz, 1H), 4.46-4.56 (m, 1H), 3.84 (dd, J=80.56, 15.12 Hz, 2H), 3.15 (dd, J=11.55, 6.05 Hz, 1H), 2.71 (dd, J=11.55, 8.80 Hz, 1H), 2.49 (s, 3H), 1.46 (s, 18H). ¹³C NMR (126 MHz, CDCl₃) ppm 157.78, 154.91, 150.59, 141.51, 139.60, 136.19, 133.48, 132.47, 130.24, 128.18, 127.84, 127.67, 127.63, 127.13, 126.08, 125.77, 125.63, 125.17, 125.07, 125.01, 83.92, 61.43, 58.44, 46.00, 45.90, 27.88.

Preparation of (S)—N,N-di-tert-butyl-(6-(2-methyl-4-(2-naphthyl)-1,2,3,4-tetrahydro-7-isoquinolinyl)-3-pyridazinyl)imidodicarbonate (Compound 12)

Scaled-up procedure: A solution of Compound 9 (1.18 kg, 1.0 equiv) in DMSO (16.5 L) was stirred at ambient temperature in a 50-L jacketed reactor as bis-pinacolato diboron (0.85 kg, 1.2 equiv) and KOAc (0.82 kg, 3.0 equiv) were added. The heterogeneous mixture was sparged with a strong stream of nitrogen for 1.5 hours. PdCl₂(dppf) (60 g, 0.025 equiv) was then added and the mixture was heated and stirred at 85° C. under nitrogen. After 5 hours, HPLC analysis indicated the reaction had stalled at ˜67% conversion, so an additional 10 g of PdCl₂(dppf) was added. After 2 h, the reaction had again stalled at 75% conversion. The solution was sparged with N₂ for 30 min, and sparging was continued throughout the rest of the reaction. An additional 10 g of PdCl₂(dppf) was added, and the reaction was complete within 2.5 h to afford a reaction mixture containing Compound 10. A solution of Cs₂CO₃ (2.74 kg, 3.0 equiv) in DI water (4.2 L) that had been sparged with a strong stream of N₂ for 1.5 hours was then added in one portion. A slurry of Compound 11 (1.15 kg, 1.25 equiv) in DMSO (6.5 L) that had been sparged with a strong stream of N₂ for 1.5 hours was then added in one portion (delayed exotherm). A final charge of PdCl₂(dppf) (60 g) was added, and the reaction mixture was stirred at 85° C. for 12 h and then cooled to 25° C. DI water (5.0 L) was added, and after stirring for 1 hour, the mixture was filtered to give a brown solid, which was conditioned under N₂ overnight.

The filter cake was dissolved in DCM (18 L) and the organic layer was washed with a 10% aqueous LiCl solution (18 L) and a 10% aqueous NH₄OH solution (18 L). The DCM layer was concentrated under reduced pressure to leave a brown solid. MeOH (6 L) was added and the slurry was stirred and heated at 55° C. for 1 hour. It was then cooled to 25° C. and EtOAc (12 L) was added. The resulting slurry was stirred for 1 hour, filtered, and the filter cake was conditioned under N₂ overnight to give 750 g of a grey solid. ICP analysis indicated the palladium content was ˜2300 ppm. The solid was then dissolved in DCM (3.75 L) and Si-thiol (1.50 kg, 2 wt equiv, Silicycle lot #10347) was added. The mixture was vigorously stirred at 30-35° C. for 4.5 hours. The mixture was cooled to room temperature and then filtered. The solid Si-thiol was then rinsed with DCM (7.5 L) and the combined dark brown filtrates were transferred to a Rotovap bulb through two 1.2 micron filters and concentrated under reduced pressure to give an off-white solid. ICP analysis indicated the palladium content was 160 ppm. The batch was re-dissolved in DCM (3.75 L) and Si-thiol (1.50 kg, 2 wt equiv) was added. After stirring for 4.5 hours at 30-35° C., the mixture was cooled to room temperature and filtered. The solid Si-thiol was rinsed with DCM (7.5 L), and the combined yellow filtrates were transferred to a Rotovap bulb through a 1.2 micron filter and concentrated under reduced pressure to give an off-white solid. ICP analysis indicated the palladium content was 3 ppm. EtOAc (4.2 L) was then added to the solid and the resulting slurry was stirred at ambient temperature for 1 hour and then filtered. The filter cake was rinsed with EtOAc (500 mL). The filter cake was conditioned under N₂ for 2 days to give 715 g of a Compound 12 as a white solid in 47% yield and >99% purity. ¹H NMR (500 MHz, d-DMSO) δ 8.31 (d, J=9.1 Hz, 1H), 8.02 (d, J=1.3 Hz, 1H), 7.87 (m, 5H), 7.79 (s, 1H), 7.48 (m, 2H), 7.39 (dd, J=8.5, 1.5 Hz, 1H), 7.01 (d, J=8.2 Hz, 1H), 4.49 (t, J=6.3 Hz, 1H), 3.78 (m, 2H), 3.02 (dd, J=11.5, 6.6 Hz, 1H), 2.73 (dd, J=11.4, 7.1 Hz, 1H), 2.39 (s, 3H), 1.41 (s, 18H).

Preparation of (S)-2-methyl-4-(naphthalen-2-yl)-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1,2,3,4-tetrahydroisoquinoline (Compound 10)

Alternative procedure: To a mixture of the triflate Compound 9 (99.0 mmol), bis(pinacolato)diboron (30.2 g, 118.8 mmol) and potassium acetate (29.1 g, 297.0 mmol) was added DMSO (725 mL). The resulting solution was purged with argon for 10 min, and then dichloro[1,1′-bis(diphenylphosphino)ferrocene]palladium(II) dichloromethane adduct (6.47 g, 7.92 mmol) was added. The reaction solution was degassed again with argon for 5 min, heated at 82° C. (oil bath) for 1 h and then cooled to room temperature and poured into water (1.0 L). The mixture was extracted with ethyl acetate (800 mL) and the organic extract was separated and washed with water (2×) and brine, dried over sodium sulfate and concentrated in vacuo. The crude boronate ester Compound 10 (48.0 g), obtained as a brown foam, was used in the next step without further purification: ESI MS m/z 400 [M+H]⁺.

Preparation of (5)-6-(2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinolin-7-yl)pyridazin-3-amine (Compound 2)

Alternative procedure directly from 3-amino-6-chloropyridazine: To a mixture of the boronate ester Compound 10 (23.0 g, 47.4 mmol), 3-amino-6-chloropyridazine (9.2 g, 71.1 mmol) and cesium carbonate (46.3 g, 142.2 mmol) were added DMF (464 mL) and water (116 mL). The reaction solution was flushed with argon for 10 min, and then dichloro[1,1′-bis(diphenylphosphino)ferrocene]palladium(II) dichloromethane adduct (3.9 g, 4.74 mmol) was added. The mixture was flushed with argon for 5 min and heated at 80° C. for 1 h. The reaction solution was cooled to room temperature, diluted with ethyl acetate, washed with 1:1 brine and water (2×), dried over sodium sulfate and concentrated in vacuo. The crude product was purified by flash column chromatography (99:0.9:0.1 to 94:5.4:0.6 ethyl acetate/methanol/concentrated ammonium hydroxide). This partially purified product (14.8 g as a brown solid) was stirred with ethyl acetate (120 mL) under argon for 12 h and filtered to give Compound 2 (12.5 g, 72%) as a brown solid: ¹H NMR (500 MHz, CDCl₃) δ 7.82-7.76 (m, 4H), 7.71 (s, 1H), 7.61-7.57 (m, 2H), 7.47-7.43 (m, 211), 7.30 (dd, J=8.0, 1.5 Hz, 1H), 6.99 (d, J=8.0 Hz, 1H), 6.80 (d, J=9.5 Hz, 1H), 4.71 (br s, 2H), 4.50 (t, J=7.0 Hz, 1H), 3.89 (d, J=15.0 Hz, 1H), 3.74 (d, J=14.5 Hz, 1H), 3.14 (dd, J=11.5, 6.0 Hz, 1H), 2.70 (dd, J=11.5, 9.0 Hz, 1H), 2.48 (s, 3H); ESI MS m/z 367 [M+H]⁺.

Preparation of (S)-6-(2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinolin-7-yl)pyridazin-3-amine dihydrochloride (Compound 13)

Compound 12 (193 g, 341 mmol) was dissolved in 2.5 M hydrochloride in ethanol (1088 ml, 2720 mmol). The solution was heated at 75° C. for 1 h. The resulted suspension was cooled to room temperature and diluted with EtOAc (2 L). The white solid was collected by filtration, washed with EtOAc (1 L). The white solid was dried at 40° C. overnight under reduced pressure to give Compound 13 (143 g, 96% yield, 99.8% purity): ¹H NMR (500 MHz, DMSO-d₆) δ ppm: 8.77 (s-broad, 2H); 8.37 (d, J=9.71 Hz, 1H); 7.95 (overlap, 1H); 7.94 (m, 2H); 7.94 (overlap, 1H); 7.91 (s, 1H); 7.76 (d, J=8.01 Hz, 1H); 7.66 (d, J=9.71 Hz, 1H); 7.56 (m, 1H); 7.55 (m, 1H); 7.33 (broad, 1H); 6.94 (broad, 1H); 4.92 (m, 1H); 4.66 (s-broad, 2H); 3.85 (m, 1H); 3.73 (m, 1H); 2.97 (s, 3H). HRMS [M+H]⁺=367.19202.

Preparation of (S)-6-(2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinolin-7-yl)pyridazin-3-amine (Compound 2)

A solution of Compound 13 (30.0 g, 0.68 mmol,) in 1:1 (v/v) MeOH/H₂O (900 mL) was filtered through a glass-sintered funnel. The filtrate was then stirred at room temperature as a saturated solution of aqueous NaHCO₃ (45 mL) was slowly added over 30 minutes, causing the solution to turn cloudy. Previously prepared seed crystals (0.10 g,) were then added to the batch in one portion. Additional saturated aqueous NaHCO₃ (555 mL) was added to the reaction mixture over 1.5 h. The slurry was filtered to afford a wet cake. The wet filter cake was then suspended in 8:2 (v/v) H₂O/MeOH (250 mL) and the resulting slurry was stirred for 3 hours and then filtered. The filter cake was washed with 8:2 (v/v) H₂O/MeOH (100 mL) and the obtained white solid was dried in vacuo at 50° C. for 30 h to give Compound 2 (23.2 g, 93% yield): ¹H NMR (d₆-DMSO, 300 MHz) δ 7.80-7.90 (m, 3H), 7.74-7.78 (m, 3H), 7.65 (dd, J=8.6; 2.1 Hz, 1H), 7.43-7.53 (m, 2H), 7.38 (dd, J=8.6; 2.1 Hz, 1H), 6.90 (d, J=8.0 Hz, 1H), 6.83 (d, J=9.1 Hz, 1H), 6.45 (s, 2H), 4.43 (t, J=5.9 Hz, 1H), 3.73 (s, 2H), 3.00 (dd, J=10.7, 5.4 Hz, 1H), 2.70 (dd, J=11.3; 7.5 Hz, 1H), 2.37 (s, 3H); ¹³C NMR (75 MHz, DMSO) ppm 159.69, 149.65, 142.55, 136.95, 135.62, 134.79, 132.93, 131.83, 129.47, 127.67, 127.46, 127.40, 127.28, 127.16, 125.98, 125.47, 125.15, 123.32, 123.06, 114.12, 60.63, 57.82, 45.55, 44.69, 40.34.

Preparation of (S)-6-(2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinolin-7-yl)pyridazin-3-amine dihydrochloride (Compound 13)

Scaled-up procedure: A mixture of Compound 12 (750 g, 1.0 equiv) in IPA (3.75 L) was stirred at room temperature as 5-6 N HCl in IPA (3.75 L,) was added over 5 minutes (slightly exothermic). The mixture was then heated to 70° C. and held for 18 h, during which time the mixture became a homogeneous yellow solution, and then a white slurry. HPLC analysis indicated the reaction was complete. The mixture was cooled to 25° C. and EtOAc (8 L) was then added in one portion. After stirring for 1 hour, the mixture was filtered to give 555 g of a Compound 13 as a white solid in 95% yield, and with >99% purity. ¹H NMR (500 MHz, d-DMSO) δ 12.05 (br s, 1H), 8.83 (br s, 2H), 8.38 (d, J=9.7 Hz, 1H), 7.94 (m, 5H), 7.76 (d, J=8.1 Hz, 1H), 7.69 (d, J=9.7 Hz, 1H), 7.55 (m, 2H), 7.33 (s, 1H), 6.93 (d, J=5.3 Hz, 1H), 4.92 (m, 1H), 4.68 (br s, 2H), 3.85 (m, 1H), 3.76 (m, 1H), 3.55 (br s, 1H), 2.97 (s, 3H).

Preparation of (S)-6-(2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinolin-7-yl)pyridazin-3-amine dihydrochloride (Compound 13)

Alternative procedure for preparation of Compound 13, bis-HCl salt, from Compound 2, Form N-1 free base: To a solution of Compound 2 (35.9 g, 98.0 mmol) in ethanol (750 mL) at room temperature was added concentrated HCl (28.7 mL) via additional funnel. The solution was heated at 80° C. and additional EtOH (500 mL) and water (55 mL) were added. After all the additions, the reaction mixture was stirred at 80° C. for 30 min upon which all solids dissolved. The solution was then filtered and the filtrate was allowed to cool to room temperature and stand overnight. The precipitate formed was collected by filtration and dried at 40° C. in vacuo for 5 h to give the desired bis-HCl salt Compound 13 (28.7 g) as an off-white solid. ¹H NMR (500 MHz, DMSO-d₆) δ ppm: 8.77 (s-broad, 2H); 8.37 (d, J=9.71 Hz, 1H); 7.95 (overlap, 1H); 7.94 (m, 2H); 7.94 (overlap, 1H); 7.91 (s, 1H); 7.76 (d, J=8.01 Hz, 1H); 7.66 (d, J=9.71 Hz, 1H); 7.56 (m, 1H); 7.55 (m, 1H); 7.33 (broad, 1H); 6.94 (broad, 1H); 4.92 (m, 1H); 4.66 (s-broad, 2H); 3.85 (in, 1H); 3.73 (m, 1H); 2.97 (s, 3H). HRMS [M+H]⁺=367.19202.

Preparation of (S)-6-(2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinolin-7-yl)pyridazin-3-amine (Compound 2)

A solution of Compound 13 (550 g, 1.0 equiv) in 1:1 MeOH/DI water (16.5 L) was passed through a 1.2 micron in-line filter. The solution was stirred at ambient temperature as a 10% aq. NaHCO₃ solution was slowly added. The batch became cloudy after 350 mL of the NaHCO₃ solution had been added. Seed crystals (10.5 g) were then added, and the mixture was stirred for an additional 1 hour. More of the NaHCO₃ solution (4 L) was added over 40 minutes. After the addition was complete, the mixture was stirred for 2 hours and then filtered. After conditioning on the filter under N₂ for 1 hour, the wet filter cake was re-suspended in 8:2 DI water/MeOH (5.5 L), stirred for 2 hours, and then filtered. The filter cake was conditioned under N₂ for 48 hours and then dried in vacuo at 35° C. for 48 hours to give 450 g of the Compound 2 as a white solid in 96% yield and >99% purity.

Examples for Synthesis Scheme 3: Asymmetric Synthesis of Compound 7

Preparation of 2-bromo-5-methoxybenzaldehyde (Compound 19)

To a solution of m-anisaldehyde (55.4 g, 0.41 mol) in DMF (400 mL) was added a solution of N-bromosuccinimide (124.0 g, 0.69 mol) dropwise at room temperature. After the addition, the reaction solution was stirred at room temperature for 12 h, then poured into a mixture of ice and water and stirred for 10 min. The precipitate was collected by filtration and dissolved in ethyl acetate. The resulting solution was washed with water (2×) and brine, dried over sodium sulfate and concentrated in vacuo to give Compound 19 (76.4 g, 87%) as an off-white solid: ¹H NMR (CDCl₃, 500 MHz) δ 10.32 (s, 1H), 7.53 (d, J=8.5 Hz, 1H), 7.42 (d, J=3.5 Hz, 1H), 7.04 (dd, J=9.0, 3.0 Hz, 1H), 3.85 (s, 3H).

Preparation of 2-(2-bromo-5-methoxyphenyl)-1,3-dioxolane (Compound 20)

To a solution of Compound 19 (50.0 g, 0.23 mol) in toluene (650 mL) were added ethylene glycol (14.2 mL, 0.26 mol) and camphorsulfonic acid (10.7 g, 46 mmol). The reaction solution was heated under reflux with a Dean-Stark trap for 6 h and then cooled to room temperature and diluted with ethyl acetate (300 mL). The resulting solution was washed with aqueous saturated sodium bicarbonate and brine, dried over sodium sulfate and concentrated in vacuo to give Compound 20 (61.5 g, quantitative) as a yellow oil: ¹H NMR (CDCl₃, 500 MHz) δ 7.44 (d, J=8.5 Hz, 1H), 7.15 (d, J=3.5 Hz, 1H), 6.79 (dd, J=8.5, 3.0 Hz, 1H), 6.04 (s, 1H), 4.18-4.06 (m, 4H), 3.81 (s, 3H).

Preparation of (R,E)-3-(3-(2-(1,3-dioxolan-2-yl)-4-methoxyphenyl)acryloyl)-4-phenyloxazolidin-2-one (Compound 21)

A mixture of Compound 20 (2.6 g, 10.0 mmol), (R)-3-acryloyl-4-phenyloxazolidin-2-one (2.2 g, 10.0 mmol), tri-o-tolyl phosphine (0.30 g, 1.0 mmol) and palladium acetate (0.11 g, 0.5 mmol) in triethylamine (35 mL) under argon was stirred under reflux for 90 min. The resulting reaction mixture was cooled to room temperature and concentrated in vacuo. The residue obtained was purified by flash column chromatography (hexanes/ethyl acetate 95:5 to 60:40) to give Compound 21 (3.2 g, 81%) as a light yellow oil: ¹H NMR (500 MHz, CDCl₃) δ 8.19 (d, J=15.5 Hz, 1H), 7.81 (d, J=15.5 Hz, 1H), 7.40 (d, J=8.5 Hz, 1H), 7.41-7.30 (m, 5H), 7.17 (d, J=3.0 Hz, 1H), 6.91 (dd, J=8.5, 3.0 Hz, 1H), 6.01 (s, 1H), 5.54 (dd, J=9.0, 3.5 Hz, 1H), 4.73 (t, J=9.0 Hz, 1H), 4.30 (dd, J=9.0, 4.0 Hz, 1H), 4.32-4.28 (m, 2H), 4.13-4.10 (m, 2H), 3.85 (s, 3H).

Preparation of (R)-3-((S)-3-(2-(1,3-dioxolan-2-yl)-4-methoxyphenyl)-3-(naphthalen-2-yl)propanoyl)-4-phenyloxazolidin-2-one (Compound 22)

To a solution of copper(I) bromide-dimethyl sulfide complex (1.43 g, 6.9 mmol) in anhydrous THF (33 mL) and dimethyl sulfide (16.5 mL) at −78° C. was added 2-naphthylene magnesium bromide (27.3 mL, 0.5 M in THF) slowly via syringe. After the addition, the reaction solution was stirred at −40° C. for 30 min, and then re-cooled to −78° C. A solution of Compound 21 (1.8 g, 4.6 mmol) in THF (24 mL) was then added via syringe. The reaction mixture was slowly warmed to room temperature before it was quenched with aqueous ammonium chloride at 0° C. and extracted with ethyl acetate (2×). The combined organic extract was washed with 1:1 water/brine, dried over sodium sulfate and concentrated in vacuo. The residue obtained was purified by flash column chromatography (hexanes/ethyl acetate 95:5 to 55:45) to give Compound 22 (2.15 g, 85%) as an off-white foam: ¹H NMR (CDCl₃, 500 MHz) δ 7.72-7.70 (m, 2H), 7.69-7.63 (m, 2H), 7.46-7.40 (m, 2H), 7.37 (d, J=8.5 Hz, 1H), 7.24 (d, J=8.5 Hz, 1H), 7.17-7.11 (m, 2H), 7.04 (t, J=7.5 Hz, 2H), 6.99 (d, J=7.5 Hz, 2H), 6.81 (s, J=8.5 Hz, 1H), 6.09 (s, 1H), 5.34-5.30 (m, 2H), 4.59 (t, J=8.5 Hz, 1H), 4.16-4.14 (m, 3H), 4.06-4.01 (m, 3H), 3.79 (s, 3H), 3.60 (dd, J=16.5, 8.5 Hz, 1H).

Preparation of (S)-3-(2-(1,3-dioxolan-2-yl)-4-methoxyphenyl)-3-(naphthalen-2-yl)propanoic acid (Compound 23)

To a solution of Compound 22 (0.55 g, 1.0 mmol) in a mixture of THF (12 mL) and water (4 mL) at 0° C. was added hydrogen peroxide (0.41 mL, 30% in water), followed by lithium hydroxide (48 mg, 2.0 mmol) in water (2.5 mL). The reaction solution was stirred at 0° C. for 1 h and room temperature for 30 min. A solution of sodium sulfite (0.78 g) in water (5 mL) was then added. After stirring at 0° C. for 10 min, the mixture was concentrated in vacuo to remove the organic solvent. The remaining aqueous solution was diluted with aqueous sodium hydroxide and extracted with dichloromethane. The basic aqueous layer was separated, neutralized with aqueous ammonium chloride to pH 6-7 and then extracted with dichloromethane (3×). The combined organic extract was dried over sodium sulfate and concentrated in vacuo to give Compound 23 (0.41 g, crude), which was used in the next step without further purification: ¹H NMR (500 MHz, CDCl₃) δ 7.56-7.70 (m, 4H), 7.48-7.33 (m, 3H), 7.13 (d, J=2.5 Hz, 1H), 7.08 (d, J=8.5 Hz, 1H), 6.80 (dd, J=9.0, 3.0 Hz, 1H), 6.08 (s, 1H), 5.18 (dd, J=9.0, 7.0 Hz, 1H), 4.21-4.00 (m, 4H), 3.77 (s, 3H), 3.20 (dd, J=16.0, 9.0 Hz, 1H), 3.12 (dd, J=16.0, 7.0 Hz, 1H).

Preparation of (S)-methyl 2-(2-(1,3-dioxolan-2-yl)-4-methoxyphenyl)-2-(naphthalen-2-yl)ethylcarbamate (Compound 24)

To a solution of Compound 23 (0.38 g, 1.0 mmol) and triethylamine (0.15 mL, 1.0 mmol) in toluene (10 mL) at 85-90° C. was added diphenylphosphorylazide (0.21 mL, 1.0 mmol) via syringe. The reaction mixture was stirred for 30 min, then it was cooled to 50° C. and methanol (0.30 mL, 7.5 mmol) was added to it. The resultant solution was stirred at 50° C. for 14 h, then cooled to room temperature, diluted with ethyl acetate and washed with aqueous ammonium chloride. The organic extract was dried over sodium sulfate and concentrated in vacuo. Purification by flash column chromatography (hexanes/ethyl acetate 95:5 to 50:50) gave Compound 24 (0.24 g, 59%) as a white foam: ¹H NMR (500 MHz, CDCl₃) δ 7.81-7.72 (m, 4H), 7.48-7.42 (m, 2H), 7.33 (d, J=8.5 Hz, 1H), 7.17-7.14 (m, 2H), 6.84 (dd, J=8.5, 2.5 Hz, 1H), 6.05 (s, 1H), 5.22 (br s, 1H), 4.81 (t, J=8.0 Hz, 1H), 4.22-4.07 (m, 4H), 3.98-3.87 (m, 2H), 3.79 (s, 3H), 3.71-3.52 (m, 3H).

Preparation of (5)-methyl 7-methoxy-4-(naphthalen-2-yl)-3,4-dihydroisoquinoline-2(1H)-carboxylate (Compound 25)

To a solution of Compound 24 (0.10 g, 0.25 mmol) in 1,4-dioxane (10 mL) at 0° C. was added concentrated HCl (0.8 mL). The reaction solution was stirred at room temperature for 20 min, and then quenched with aqueous sodium bicarbonate and extracted with dichloromethane (2×). The combined organic extract was dried over sodium sulfate and concentrated in vacuo. The residue obtained was dissolved in a mixture of ethanol (30 mL) and trifluoroacetic acid (2 mL). Palladium on carbon (105 mg) was added and the reaction mixture was shaken under hydrogen (25 psi) for 15 min, then filtered through a pad of celite and concentrated in vacuo. The residue was dissolved in dichloromethane and the resulting solution was washed with aqueous sodium bicarbonate, dried over sodium sulfate and concentrated in vacuo. Purification by preparative thin layer chromatography (hexanes/ethyl acetate 75:25) provided Compound 25 (52 mg, 60%) as a colorless oil: ¹H NMR (500 MHz, CDCl₃) δ 7.82-7.74 (m, 3H), 7.62-7.51 (m, 1H), 7.47-7.44 (m, 2H), 7.24 (d, J=9.0 Hz, 1H), 6.85 (d, J=8.5 Hz, 1H), 6.80-6.68 (m, 2H), 4.83-4.60 (m, 2H), 4.40-3.90 (m, 2H), 3.81 (s, 3H), 3.76-3.42 (m, 4H); ESI MS m/z 348 [M+H]⁺.

Preparation of (S)-7-methoxy-2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinoline (Compound 7)

To a solution of Compound 25 (51 mg, 0.15 mmol) in THF (8 mL) at 0° C. was added lithium aluminum hydride (0.6 mL, 1 M in THF) dropwise. After the addition, the reaction solution was heated under reflux for 1 h, cooled to 0° C. and quenched by sequential addition of water (1.8 mL), aqueous sodium hydroxide (0.6 mL) and water (0.6 mL). The resultant mixture was stirred at 0° C. for 10 min before it was filtered. The filtrate was extracted with dichloromethane (2×). The combined organic extract was dried over sodium sulfate and concentrated in vacuo. Purification by preparative thin layer chromatography (dichloromethane/methanol/concentrated ammonia 95:4.5:0.5) provided Compound 7 (32.0 mg, 70%, AUC HPLC 96.8%, Chiralpak AD 100%) as a light yellow oil: [α]²³ _(D) +50.7° (c 0.18, methanol); ¹H NMR (500 MHz, CDCl₃) δ 7.79-7.68 (m, 3H), 7.68 (s, 1H), 7.47-7.43 (m, 2H), 7.28-7.26 (m, 1H), 6.80 (d, J=8.0 Hz, 1H), 6.65-6.62 (m, 2H), 4.39 (dd, J=8.5, 6.0 Hz, 1H), 3.78 (s, 3H), 3.77 (d, J=15.0 Hz, 1H), 3.65 (d, J=14.5 Hz, 1H), 3.09 (dd, J=11.5, 5.5 Hz, 1H), 2.64 (dd, J=11.5, 9.0 Hz, 1H), 2.44 (s, 3H); ESI MS m/z 304 [M+H]⁺. This compound co-elutes with authentic Compound 7 on Chiralpak AD (90:10:0.1 heptane: IPA: diethyl amine, 1 mL/min, RT=14.3 min. The RT of the (−)-enantiomer of Compound 7=6.2 min).

Preparation of 1-(3-bromophenyl)-N-methylmethanamine (Compound 14)

To a solution of 3-bromobenzaldehyde (138 g, 0.74 mol) in methanol (0.9 L) was added a 40% aqueous solution of methylamine (64 mL, 0.82 mol) followed by stirring at 0° C. for 1 h. Sodium borohydride (42.3 g, 1.1 mol) was added in portions at 0° C. and the reaction mixture was stirred overnight while warming to room temperature. The solution was concentrated, then diluted with water (300 mL). The resulting solution was extracted with methylene chloride (3×300 mL) and chloroform (2×300 mL). The combined organic extracts were washed with brine (2×200 mL) then dried over sodium sulfate, filtered and concentrated under reduced pressure to afford crude Compound 14 (148 g) as a clear oil, which was used in the next step without further purification: ¹H NMR (CDCl₃, 300 MHz) δ7.48 (s, 1H), 7.39-7.34 (m, 1H), 7.27-7.16 (m, 2H), 3.71 (s, 2H), 2.43 (s, 3H), 1.38 (s, 1H).

Preparation of 2-((3-bromobenzyl)(methyl)amino)-1-(naphthalen-2-yl)ethanone (Compound 15)

To a solution of Compound 14 (23.1 g, 115.5 mmol) in methylene chloride (500 mL) was added α-bromo-2′-acetonapthone (27.9 g, 110.0 mmol) and the resulting mixture was stirred at 0° C. for 1 h prior to the addition of triethylamine (15.3 mL, 47.4 mmol). The reaction mixture was stirred at 0° C. for 2 h. The resulting mixture was diluted with water (200 mL) and the aqueous phase was extracted with additional methylene chloride (2×200 mL). The combined extracts were dried over sodium sulfate, filtered and concentrated to afford Compound 15 (44.5 g) as a light yellow oil, which was used in the next step without further purification: ¹H NMR (CDCl₃, 500 MHz) δ 8.49 (s, 1H), 8.01 (dd, J=8.8, 1.8 Hz, 1H), 7.95 (d, J=8.0 Hz, 1H), 7.90-7.84 (m, 2H), 7.62-7.52 (m, 3H), 7.40 (d, J=8.0 Hz, 1H), 7.31 (d, J=8.0 Hz, 1H), 7.19 (t, J=7.7 Hz, 1H), 3.91 (s, 2H), 3.68 (s, 2H), 2.40 (s, 3H).

Preparation of 2-((3-bromobenzyl)(methyl)amino)-1-(naphthalen-2-yl)ethanol (Compound 16)

To a solution of Compound 15 (˜110 mmol) in methanol (600 mL), sodium borohydride (5.4 g, 142.8 mmol) was added in portions at 0° C. The reaction mixture was first stirred overnight while warming up to room temperature. The reaction mixture was concentrated under reduced pressure. The residue was diluted with water (200 mL) and the solution was extracted with methylene chloride (3×300 mL). The combined organic extracts were dried over sodium sulfate, filtered and concentrated to dryness under reduced pressure to afford the crude desired product Compound 16 (42.6 g) as a yellow oil, which was used without further purification in the next step: ¹H NMR (300 MHz, CDCl₃) δ 7.86-7.79 (m, 4H), 7.52-7.38 (m, 5H), 7.28-7.15 (m, 2H), 4.93 (dd, J=9.5, 4.4 Hz, 1H), 4.05 (s, 1H), 3.71 (d, J=13.3 Hz, 1H), 3.52 (d, J=13.3 Hz, 1H), 2.72-2.61 (m, 2H), 2.34 (s, 3H).

Preparation of 7-bromo-2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinoline (Compound 17)

To a solution of Compound 16 (˜110 mmol) in methylene chloride (1.0 L) was added concentrated sulfuric acid (30.0 mL, 0.56 mol) and the mixture was stirred at 0° C. for 3 h. The reaction was quenched by adding 6 N NaOH until the pH was ˜9, and the aqueous phase was extracted with additional methylene chloride (3×). The combined organic extracts were dried over sodium sulfate, filtered and concentrated. The residue was purified by flash chromatography (9:1 to 8:1 hexanes/ethyl acetate) to afford Compound 17 (15.79 g, 41% over 3 steps) as a white solid: ¹H NMR (500 MHz, CDCl₃) δ 7.82-7.70 (m, 3H), 7.66 (s, 1H), 7.49-7.41 (m, 2H), 7.28-7.20 (m, 2H), 7.16 (dd, J=8.3, 2.3 Hz, 1H), 6.75 (d, J=8.5 Hz, 1H), 4.37 (dd, J=7.5, 6.5 Hz, 1H), 3.75 (d, J=15.3 Hz, 1H), 3.62 (d, J=15.3 Hz, 1H), 3.08 (ddd, J=11.5, 6.0, 1.0 Hz, 1H), 2.64 (dd, J=11.5, 8.5 Hz, 1H), 2.43 (s, 3H). The undesired 5-bromo isomer was also obtained (11.91 g, 30% over 3 steps).

Preparation of 2-methyl-4-(naphthalen-2-yl)-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1,2,3,4-tetrahydroisoquinoline (Compound 18)

To a mixture of Compound 17 (19.3 mmol), bis(pinacolato)diboron (5.9 g, 23.2 mmol), and potassium acetate (5.7 g, 57.9 mmol) was added DMSO (140 mL). The resultant solution was purged with argon for 10 min, and then dichloro[1,1′-bis(diphenylphosphino)ferrocene]palladium(II) dichloromethane adduct (1.3 g, 1.5 mmol) was added. The reaction solution was degassed again with argon for 5 min, then heated at 80° C. (oil bath) for 1 h. The resultant solution was cooled to room temperature, diluted with ethyl acetate and washed with water and brine. The organic layer was separated, dried over sodium sulfate and concentrated under reduced pressure. The crude boronate ester 2-methyl-4-(naphthalen-2-yl)-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1,2,3,4-tetrahydroisoquinoline Compound 18 (10.0 g), obtained as a brown foam, was used in the next step without further purification: ESI MS m/z 400 [M+H]⁺.

Preparation of rac-6-(2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinolin-7-yl)pyridazin-3-amine (rac-1)

To a mixture of Compound 18 (6.0 g, 15.0 mmol), 3-amino-6-chloropyridazine (3.0 g, 22.5 mmol) and cesium carbonate (14.7 g, 45.0 mmol) were added DMF (140 mL) and water (35 mL). The reaction solution was flushed with argon for 10 min, and then dichloro[1,1′-bis(diphenylphosphino)ferrocene]palladium(II) dichloromethane adduct (1.2 g, 1.5 mmol) was added. The resultant mixture was flushed with argon for 5 min and heated at 80° C. for 1 h. The reaction solution was then cooled to room temperature, diluted with ethyl acetate, washed with 1:1 brine and water (2×), dried over sodium sulfate and concentrated in vacuo. The crude product was purified by flash column chromatography (92:2:5.4:0.6 to 47:47:5.4:0.6 dichloromethane/ethyl acetate/methanol/concentrated ammonium hydroxide) to give rac-1 (3.2 g, 58%) as a light tan solid: ¹H NMR (500 MHz, CDCl₃) δ 7.82-7.76 (m, 4H), 7.71 (s, 1H), 7.61-7.57 (m, 2H), 7.47-7.43 (m, 2H), 7.30 (dd, J=8.0, 1.5 Hz, 1H), 6.99 (d, J=8.0 Hz, 1H), 6.80 (d, J=9.5 Hz, 1H), 4.71 (br s, 2H), 4.50 (t, J=7.0 Hz, 1H), 3.89 (d, J=15.0 Hz, 1H), 3.74 (d, J=14.5 Hz, 1H), 3.14 (dd, J=11.5, 6.0 Hz, 1H), 2.70 (dd, J=11.5, 9.0 Hz, 1H), 2.48 (s, 3H); ESI MS m/z 367 [M+H]⁺.

Preparation of (5)-6-(2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinolin-7-yl)pyridazin-3-amine (Compound 2)

Rac-1 (3.3 g) was resolved by preparative chiral HPLC (CHIRALCEL OD column, using 80:20:0.1 heptane/ethanol/diethylamine as the eluent) to give the (S)-enantiomer Compound 2 [[α]²⁵ _(D) +122.0° (c 0.15, methanol)] (1.6 g) as a light brown foam and the (R)-enantiomer [[α]²⁵ _(D) −124.3° (c 0.23, methanol)] (1.6 g) as an off-white solid.

Preparation of (S)-6-(2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinolin-7-yl)pyridazin-3-amine, L-tartrate (Compound 2, L-tartrate)

To a mixture of Compound 2, free base (1.6 g, 4.3 mmol) and L-tartaric acid (0.65 g, 4.3 mmol) were added methanol (280 mL) and water (100 mL). The reaction slurry was sonicated and heated at approximately 55° C. to give a clear solution, which was then concentrated in vacuo to about 100 mL. The resulting solution was lyophilized to give Compound 2-L-tartrate (2.18 g, 98.6%, AUC HPLC>99%) as an off-white solid: mp 153-158° C.; ¹H NMR (500 MHz, CDCl₃) δ 7.87-7.80 (m, 6H), 7.69 (dd, J=8.0, 1.5 Hz, 1H), 7.51-7.48 (m, 2H), 7.30 (dd, J=8.5, 1.5 Hz, 1H), 7.04-7.01 (m, 2H), 4.71 (dd, J=11.0, 5.5 Hz, 1H), 4.43 (s, 2H), 4.39 (d, J=16.0 Hz, 1H), 4.29 (d, J=15.5 Hz, 1H), 3.64(dd, J=11.5, 5.5 Hz, 1H), 3.37-3.30 (m, 1H), 2.85 (s, 3H); ESI MS m/z 367 [M+H]⁺; Anal. Calcd. For C₂₄H₂₂N₄.C₄H₆O₆.H₂O: C, 62.91; H, 5.66; N, 10.48. Found: C, 62.81; H 5.73; N, 10.30.

Preparation of (S)-6-(2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinolin-7-yl)pyridazin-3-amine, L-tartrate (Compound 2, L-tartrate salt)

Alternative procedure: To a slurry of Compound 2, free base (1.5 g, 4.1 mmol) in methanol (80 mL) was added a solution of L-tartaric acid (0.63 g, 4.2 mmol) in methanol (15 mL) and water (10 mL). The reaction slurry became a clear solution after heating under reflux. The resulting solution was then cooled to 0° C. while stirring and precipitation occurred. The precipitate obtained was collected by filtration. This solid was re-crystallized twice from methanol (150 mL) and water (20 mL). The resulting solid was dissolved in methanol (25 mL) and water (100 mL), and the solution was lyophilized to give the L-tartrate salt of Compound 2, (1.4 g, 65%, AUC HPLC>99%) as a white solid: [α]²³ _(D) +79.1° (c 0.15, methanol); ¹H NMR (500 MHz, CDCl₃) δ 7.87-7.80 (m, 6H), 7.69 (dd, J=8.0, 1.5 Hz, 1H), 7.51-7.48 (m, 2H), 7.30 (dd, J=8.5, 1.5 Hz, 1H), 7.04-7.01 (m, 2H), 4.71 (dd, J=11.0, 5.5 Hz, 1H), 4.43 (s, 2H), 4.39 (d, J=16.0 Hz, 1H), 4.29 (d, J=15.5 Hz, 1H), 3.64(dd, J=11.5, 5.5 Hz, 1H), 3.37-3.30 (m, 1H), 2.85 (s, 3H); ESI MS m/z 367 [M+H]⁺.

Preparation of (S)-7-(6-chloropyridazin-3-yl)-2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinoline (Compound 31)

A solution of the crude Compound 10 (12.5 g, prepared from 15.1 g of Compound 9 using a similar procedure described earlier for the synthesis of Compound 10), 3,6-dichloropyridazine (5.60 g, 37.6 mmol), and sodium carbonate solution (40 mL. 2M, 80.0 mmol) in DMF (25 mL) was degassed with argon. To this mixture was added dichloro[1,1′-bis(diphenylphosphino)ferrocene]palladium(II) dichloromethane adduct (2.6 g, 3.1 mmol). The resulting mixture was degassed with argon and then heated at 90° C. for 3 h. After cooling, the solution was quenched by adding water. The solution was extracted into dichloromethane (3×). The combined organic extracts were dried over magnesium sulfate, filtered, and concentrated in vacuo. Purification by column chromatography (100:0 to 0:100 hexanes/ethyl acetate) provided the Compound 31 as a light-red solid (6.23 g, 51%); ¹H NMR (500 MHz, CDCl₃) δ 8.29 (d, J=9.0 Hz, 1H), 7.99 (d, J=9.0 Hz, 2H), 7.88-7.83 (m, 4H), 7.79 (s, 1H), 7.50-7.47 (m, 2H), 7.38 (dd, J=8.5, 1.5 Hz, 1H), 7.00 (d, J=0.8 Hz, 1H), 5.00-4.90 (m, 1H), 4.50-4.40 (m, 1H), 4.25-4.15 (m, 1H), 3.60-3.50 (m, 1H), 3.15-3.05 (m, 1H), 2.84 (s, 3H). ESI MS m/z 386 [M+H]⁺.

Preparation of (S)—N-(2,4-dimethoxybenzyl)-6-(2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinolin-7-yl)pyridazin-3-amine (compound 32)

A solution of Compound 31 (300 mg, 0.76 mmol) in 2,4-dimethoxybenzylamine (2.0 mL, 13.3 mmol) was heated at 80° C. for 2 days. After cooling to room temperature, the solution was purified using column chromatography (50:50:0 to 0:95:5 hexanes/ethyl acetate/triethylamine) to provide Compound 32 as an oil. (0.19 g, 48%) ¹H NMR (500 MHz, CDCl₃) δ 7.85-7.75 (m, 4H), 7.71 (s, 1H), 7.60-7.40 (m, 4H), 7.35-7.25 (m, 2H), 6.96 (d, J=8.0 Hz, 1H), 6.67 (d, J=8.0 Hz, 1H), 6.48 (s, 1H), 6.44-6.42 (m, 1H), 5.20-5.10 (m, 1H), 4.58 (d, J=6.0 Hz, 1H), 4.50-4.40 (m, 1H), 3.90-3.80 (m, 1H), 3.86 (s, 3H), 3.80 (s, 3H), 3.72 (d, J=15.0 Hz, 1H), 3.20-3.10 (m, 1H), 2.69 (dd, J=11.5, 8.5 Hz, 1H), 2.47 (s, 3H); ESI MS m/z 517 [M+H]⁺.

Preparation of (S)-6-(2-methyl-4-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinolin-7-yl)pyridazin-3-amine (Compound 2) and the maleic acid salt of Compound 2

A solution of Compound 32 (0.19 g, 0.37 mmol) was reacted with trifluoroacetic acid (3 mL) in DCM (10 mL). After stirring at room temperature for 12 h, the reaction was quenched by adding saturated sodium bicarbonate solution. The product was extracted into methylene chloride. The organic phase was dried over magnesium sulfate, filtered, and concentrated. Purification by column chromatography (100:0 to 50:50 methylene chloride/methanol) afforded Compound 2 as an oil. (0.11 g, 85%). ¹H NMR (500 MHz, CDCl₃) δ 7.90-7.80 (m, 4H), 7.72 (s, 1H), 7.60-7.50 (m, 2H), 7.50-7.40 (m, 2H), 7.30-7.25 (m, 1H), 6.98 (d, J=7.5 Hz, 1H), 6.82 (d, J=8.5 Hz, 1H), 5.00-4.90 (m, 1H), 4.60-4.50 (m, 1H), 4.00-3.90 (m, 1H), 3.90-3.70 (m, 2H), 3.25-3.15 (m, 1H), 2.85-2.75 (m, 1H), 2.54 (s, 3H); ESI MS m/z 367 [M+H]⁺.

A solution of Compound 2 (0.11 g, 0.31 mmol) in methanol (2 mL) and maleic acid (40 mg, 0.34 mmol) was stirred at room temperature. The solvent was evaporated. Lyophilization from acetonitrile (0.5 mL)/water (0.5 mL) yielded the correspondent maleic acid salt of Compound 2 (88 mg, 98%, 98.5% AUC HPLC) as a brown solid: m.p. 89-91° C.; ¹H NMR (CD₃OD, 500 MHz) δ 8.14 (d, J=9.5 Hz, 1H), 8.00-7.80 (m, 6H), 7.50-7.55 (m, 2H), 7.38 (d, J=10.0 Hz, 1H), 7.32 (dd, J=8.5, 1.5 Hz, 1H), 7.10 (d, J=3.0 Hz), 6.25 (s, 3H), 4.90-4.85 (m, 1H), 4.68 (s, 2H), 3.94-3.92 (m, 1H), 3.70-3.60 (m, 1H), 3.11 (s, 3H); ESI MS m/z 367 [M+H]⁺.

Preparation of N,N,-ditert-butoxycarbonyl, 3-(6-aminopyridazin-3-yl)benzaldehyde, Compound 26

Compound 11 (5.00 g, 13.2 mmol) was dissolved in DMSO (75 mL), and treated successively with 3-formylphenyl boronic acid (2.30 g; 15.3 mmol), cesium carbonate (15.62 g; 47.46 mmol), and water (23 mL). The reaction mixture was degassed with nitrogen for 20 minutes prior to the addition of the catalyst, 1,1′-bis(diphenylphosphino)ferrocene)palladium(II) chloride (0.47 g; 0.63 mmoles). The reaction mixture was purged with nitrogen for 10 minutes and then heated at 85° C. for two days. After an additional two days at ambient temperature the reaction mixture was diluted with EtOAc and water filtered through a pad of celite to remove dark colored particulates. The isolated dark brown organic layer was washed with 50% brine, dried over MgSO₄, filtered, and concentrated under reduced pressure to afford 5.7 g of a dark brown residue. The residue was purified by flash column chromatography (eluting 0-100% EtOAc/heptane) and the product rich fractions were combined, concentrated under reduced pressure to afford 3.8 g (96%) of a product that upon further analysis was the mono-Boc species. Reprotection of this product to afford bis-Boc compound was achieved with the following procedure.

To a solution of the mono-Boc species (0.504 g, 1.68 mmol) and 4-DMAP (0.020, 1.7 mmol) in DMF (4 mL) was added a solution of (Boc)₂O (0.379 g, 1.68 mmol) in DMF (4 mL). The reaction mixture was warmed to 50-55° C. for 1.5 hours. The reaction mixture was added dropwise to water (8 mL) to afford a white precipitate. Following an additional 8 mL of water, the slurry was filtered, the isolated solids were washed with 25% DMF(aq), by volume, followed by water. Further drying under vacuum afford Compound 26 (0.561 g, 1.40 mmol, 83% yield) as an off-white solid. ¹H NMR (400 MHz, d6-DMSO) major rotamer δ 10.16 (s, 1H), 8.74 (s, 1H), 8.51 (d, J=9.0 Hz, 1H), 8.48 (d, J=9.1 Hz, 1H), 8.08 (d, J=7.9 Hz, 1H), 8.00 (d, J=12.1 Hz, 1H), 7.82 (dd, J=7.6, 7.8 Hz, 1H), 1.42 (s, 18H). ¹³C NMR (100 MHz, d6-DMSO) ppm 27.4, 83.4, 126.5, 127.1, 128.3, 130.0, 130.6, 132.7, 136.1, 136.9, 150.2, 155.5, 156.5, 193.0. ESI MS m/z 400.19 [M+H]⁺.

Preparation of N,N,-ditert-butoxycarbonyl, 2-((3-(6-aminopyridazin-3-yl))(methyl)amino)-1-(naphthalen-2-yl)ethanol (compound 29)

A slurry of Compound 26 (1.0 g, 2.5 mmol) in methanol (10.0 mL), as a mixture on mono and bis-Boc derivatives, was cooled to <5° C. in using an ice bath. A methanolic solution of methylamine (1.3 mL, 2.60 mmol, 2M/MeOH) was added to the white slurry, and the cooled reaction mixture was stirred for 2 hours prior to the addition of sodium borohydride (0.1 g; 2.6 mmoles). After 1.5 hours the reaction mixture was quenched with water, while maintaining temp<25° C., and concentrated under reduced pressure using a rotary evaporator. The residue was dissolved with EtOAc, and the resulting organic layer was washed with brine, and dried over MgSO4. Concentration of the filtered organic layer afforded Compound 27 as a colorless oil which was used without further purification.

1-Bromo acetonaphthanone (0.265 g; 1.04 mmoles) was added to a crude solution of compound 27 (0.50 g; 1.37 mmol) in DCM (15 mL) at 0° C. After 10 minutes triethylamine (0.145 mL; 1.04 mmol) was added and the reaction mixture was warmed to room temperature. After an additional three hours the reaction mixture was washed two times with water, dried over MgSO4. The filtered organic layers were concentrated under reduced pressure to afford Compound 28 as yellow foam which was used without further purification.

Sodium borohydride (0.04 g, 1.04 mmol) was added to a cold solution (, 5 C) of compound 28 (0.50 g, 1.04 mmol) in MeOH (7 mL). After 45 minutes the reaction mixture was quenched with water, and warmed to room temperature and held overnight. The reaction mixture was concentrated under reduced pressure using a rotary evaporator. The residue was partioned between water and dichloromethane, the aqueous layer was back extracted with dichloromethane. The combined organic phases were dried over MgSO4, filtered, and concentrated in vacuo to afford a yellow foam 0.53 g. (106%) Approximately 100 mg of the crude material was purified by flash column chromatography (EtOAc/heptane) to afford 53 mg of the desired product. Analytical analysis indicated the material to be the mono-Boc intermediate of Compound 29. 1H NMR (400 MHz, d6-DMSO) major rotamer δ 10.54 (s, 1H), 8.09 (d, J=9.4 Hz, 1H), 8.01 (d, J=9.6 Hz, 1H), 7.92-7.93 (m, 2H), 7.81-7.86 (m, 4H), 7.45-7.50 (m, 3H), 7.40 (dd, J=7.9, 8.0 Hz, 1H), 7.33 (d, J=7.6 Hz, 1H), 5.24 (d, J=3.7 Hz, 1H), 4.94 (dd, J=6.4, 9.3 Hz, 1H), 3.70 (d, J=13.4 Hz, 1H), 3.63 (d, J=13.4 Hz, 1H), 2.70 (dd, J=7.2, 12.8 Hz, 1H), 2.64 (dd, J=5.6, 12.7 Hz, 1H), 2.29 (s, 3H), 1.52 (s, 9H). ESI MS m/z 485 [M+H]⁺.

Form N-1 was analyzed using one or more of the testing methods described below.

Single Crystal X-Ray Measurements

A Nonius Kappa CCD diffractometer equipped with graphite-monochromated Mo Kα radiation (λ=0.7107 Å) was used to collect diffraction data at the room temperature (Nonius 2001a. Data Collection Software for Nonius Kappa-CCD devices. Nonius BV, Delft, The Netherlands. Nonius 2001b; DENZO Processing Software for Nonius Kappa-CCD devices, Nonius BV, Delft, The Netherlands). The final unit cell parameters were determined using the entire data set.

All structures were solved by direct methods and refined by the full-matrix least-squares techniques, using the SHELXTL software package (Sheldrick, GM. 1997, SHELXTL. Structure Determination Programs. Version 5.10, Bruker AXS, Madison, Wis., USA.). The function minimized in the refinements was Σ_(w)(|F_(o)|−|F_(c)|)². R is defined as Σ∥F_(o)|−|F_(c)∥/ΣF_(o)| while R_(w)=[Σ_(w)(|F_(o)|−|F_(c)|)₂/Σ_(w)|F_(o)|²]^(1/2), where w is an appropriate weighting function based on errors in the observed intensities. Difference Fourier maps were examined at all stages of refinement. All non-hydrogen atoms were refined with anisotropic thermal displacement parameters. The hydrogen atoms associated with hydrogen bonding were located in the final difference Fourier maps while the positions of the other hydrogen atoms were calculated from an idealized geometry with standard bond lengths and angles. They were assigned isotropic temperature factors and included in structure factor calculations with fixed parameters.

The crystal data of the N-1 form is shown in Table 2. The fractional atomic coordinates are listed in Table 3. It should be understood by one of ordinary skill in the art that slight variations in the coordinates are possible and are considered to be within the scope the present disclosure.

TABLE 2 Crystal Data of Form N-1 Temperature room temperature Wavelength 0.71073 Å Crystal system, space group Monoclinic, P2₁ Unit cell dimensions a = 8.4299(4) Å alpha = 90° b = 6.0698(3) Å beta = 100.169(2)° c = 19.0689(12) Å gamma = 90° Volume 960.39(9) Å³ Z, Calculated density 2, 1.267 g/cm³

TABLE 3 Atomic Coordinates x y z U(eq) N1 0.3248(4) −0.7759(7) −0.0061(2) 0.0608(10) N2 0.3353(4) −0.4151(6) 0.0322(2) 0.0516(9) N3 0.2832(4) −0.2519(6) 0.07049(19) 0.0504(8) N4 −0.2362(4) 0.4479(6)   0.20586(19) 0.0525(9) C1 0.2608(5) −0.6106(7) 0.0275(2) 0.0476(9) C2 0.1165(5) −0.6421(7) 0.0547(2) 0.0476(9) C3 0.0665(5) −0.4763(7) 0.0935(2) 0.0487(9) C4 0.1596(4) −0.2835(6) 0.1041(2) 0.0439(8) C5 0.1240(5) −0.1073(6) 0.1527(2) 0.0453(9) C6 −0.0334(4) −0.0444(6) 0.1549(2) 0.0447(9) C7 −0.0674(4) 0.1306(6) 0.1973(2) 0.0446(9) C8 −0.2368(5) 0.2120(8) 0.1916(3) 0.0556(10) C9 −0.3995(6) 0.5360(11) 0.1966(4) 0.0778(15) C10 −0.1522(5) 0.4871(7) 0.2779(2) 0.0541(10) C11 0.0289(4) 0.4359(6) 0.2862(2) 0.0463(9) C12 0.0594(4) 0.2382(7) 0.2416(2) 0.0441(8) C13 0.2163(5) 0.1695(7) 0.2403(2) 0.0541(11) C14 0.2491(5) 0.0035(8) 0.1957(2) 0.0528(11) C15 0.1013(4) 0.4074(6) 0.3638(2) 0.0439(8) C16 0.1983(5) 0.5661(6) 0.4007(2) 0.0445(9) C17 0.2648(4) 0.5393(6) 0.4738(2) 0.0450(9) C18 0.3664(5) 0.6998(7) 0.5124(2) 0.0533(10) C19 0.4321(6) 0.6659(9) 0.5822(3) 0.0681(13) C20 0.4004(6) 0.4740(9) 0.6174(2) 0.0661(13) C21 0.3015(5) 0.3166(8) 0.5816(3) 0.0611(11) C22 0.2296(4) 0.3441(7) 0.5095(2) 0.0449(9) C23 0.1271(5) 0.1861(7) 0.4707(2) 0.0529(10) C24 0.0654(5) 0.2157(7) 0.4011(2) 0.0527(10) H1A 0.4107 −0.7535 −0.0236 0.073 H1B 0.2796 −0.9034 −0.0099 0.073 H16 0.2208 0.6937 0.3773 0.053 H11 0.0810 0.5636 0.2684 0.056 H6 −0.1181 −0.1205 0.1275 0.054 H14 0.3554 −0.0346 0.1945 0.063 H24 −0.0020 0.1086 0.3769 0.063 H3 −0.0272 −0.4903 0.1126 0.058 H13 0.3012 0.2375 0.2703 0.065 H19 0.4991 0.7727 0.6068 0.082 H2 0.0579 −0.7721 0.0463 0.057 H21 0.2812 0.1886 0.6054 0.073 H20 0.4462 0.4531 0.6650 0.079 H10A −0.1992 0.3957 0.3106 0.065 H10B −0.1662 0.6399 0.2904 0.065 H23 0.1014 0.0591 0.4936 0.063 H8A −0.2964 0.1828 0.1442 0.067 H8B −0.2897 0.1348 0.2257 0.067 H18 0.3887 0.8294 0.4900 0.064 H9A −0.4538 0.4762 0.2325 0.117 H9B −0.4572 0.4962 0.1503 0.117 H9C −0.3952 0.6936 0.2008 0.117 Powder X-Ray Diffraction

X-ray powder diffraction (PXRD) data were obtained using a Bruker C2 GADDS. The radiation was Cu Kα (40 KV, 40 mA). The sample-detector distance was 15 cm. Powder samples were placed in sealed glass capillaries of 1 mm or less in diameter; the capillary was rotated during data collection. Data were collected for 3≦2θ≦35° with a sample exposure time of at least 1000 seconds. The resulting two-dimensional diffraction arcs were integrated to create a traditional 1-dimensional PXRD.

The results of the PXRD pattern and a simulated pattern calculated from the single crystal data are shown in FIG. 1.

Table 4 lists the characteristic PXRD peaks that describe Form N-1 of Compound 2.

TABLE 4 Characteristic diffraction peak positions (degrees 2θ ± 0.1) at room temperature, based on a high quality pattern collected with a diffractometer (cuKα) with a spinning capillary with 2θ calibrated with a NIST other suitable standard. N-1 4.6 9.4 10.6 14.1 15.4 18.2 19.5 Differential Scanning Calorimetry

Differential scanning calorimetry (DSC) experiments were performed in a TA Instruments™ model Q1000 or 2920. The sample (about 2-6 mg) was weighed in an pinpricked hermetically sealed aluminum pan and recorded accurately recorded to a hundredth of a milligram, and transferred to the DSC. The instrument was purged with nitrogen gas at 50 mL/min. Data were collected between room temperature and 300° C. at 10° C./min heating rate. The plot was made with the endothermic peaks pointing down.

The results are shown in FIG. 2.

Solid-State Nuclear Magnetic Resonance (SSNMR)

All solid-state C-13 NMR measurements were made with a Bruker DSX-400, 400 MHz NMR spectrometer. High resolution spectra were obtained using high-power proton decoupling and the TPPM pulse sequence and ramp amplitude cross-polarization (RAMP-CP) with magic-angle spinning (MAS) at approximately 12 kHz (A. E. Bennett et al, J. Chem. Phys., 1995, 103, 6951), (G. Metz, X. Wu and S. O. Smith, J. Magn. Reson. A,. 1994, 110, 219-227). Approximately 70 mg of sample, packed into a canister-design zirconia rotor was used for each experiment. Chemical shifts (δ) were referenced to external adamantane with the high frequency resonance being set to 38.56 ppm (W. L. Earl and D. L. VanderHart, J. Magn. Reson., 1982, 48, 35-54).

The results are shown in FIG. 3.

In a preferred aspect, Form N-1 has the properties set for the in Table 5, below.

TABLE 5 Physical and Chemical Properties Chemical name 6-[(4S)-1,2,3,4-tetrahydro-2-methyl-4-(2-naphthalenyl)-7- isoquinolinyl]-3-pyridazinamine Chemical Structure

Molecular formula C₂₄H₂₂N₄ Molecular weight 366.46 Appearance White to off-white powder Melting point/range 237°-243° C. Solution pH ~7.0 at about 1 μg/mL concentration in water pH-Solubility profile At solution pH 6.5 and above, the aqueous solubility of Compound 2 is ~1 μg or less. Aqueous solubility increases at lower pH values (15.6 mg/mL at pH 2.0 and 1.76 mg/mL at pH 4.4) Solubility profile practically insoluble: n-heptane (USP definition) very slightly soluble: acetonitrile, ethyl acetate, n-butanol slightly soluble: isopropanol, acetone, ethanol, methanol propylene glycol, dichloromethane sparingly soluble: PEG 400 soluble: N,N-dimethylacetamide, dimethylsulfoxide freely soluble: tetrahydrofuran pK_(a) 4.9 and 7.8 Distribution coefficient Log D_(o/b) = 3.10 at pH 6.5 and 3.82 at pH 7.4 Stability Compound 2 is stable up to 25° C. with protection from light.

Where noted above, publications and references, including but not limited to patents and patent applications, cited in this specification are herein incorporated by reference in their entirety in the entire portion cited as if each individual publication or reference were specifically and individually indicated to be incorporated by reference herein as being fully set forth.

While this invention has been described with an emphasis upon specific aspects, those skilled in the art will recognize that variations in the aspects disclosed may be used and that it is intended that the invention may be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications encompassed within the spirit and scope of the invention as defined by the claims that follow. For example, it should be understood that the reaction steps set forth in the appended claims need not necessarily be performed in the order in which they appear, and one skilled in the field may be able to vary the order of reaction steps. Additionally, certain reaction sequences may be performed simultaneously, or these reactions can be performed in separate steps, without departing from the spirit and scope of the invention. It is intended that all such modifications are encompassed within the scope of the appended claims. In addition, alternative process steps or process conditions effective to promote the formation of the desired compounds, e.g., different reagents, acids, salts, protecting groups, techniques, catalysts, pressures, temperatures, reaction times, and the like, are known to those skilled in the art and may be employed and are intended to be within the scope of the claims which follow. 

What is claimed is:
 1. A compound having the following formula:

where each R₅ is selected from the group consisting of t-butoxycarbonyl, carboxybenzyl, para-methoxybenzylcarbonyl, para-methoxybenzyl, 2,4-dimethoxybenzyl, benzyl, 9-fluorenylmethyloxycarbonyl, N-phthalimide, COCH₃ and COCF₃.
 2. A compound having the following formula: 